REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Charge
Introduction:
It all begins with atoms. An understanding of static electricity begins with an understanding of the atom.
Matter is made of atoms and if any sample of matter is charged, becomes charged or loses a charge,
then the explanation of what happened demands that one understand matter at the particle level.
1. Draw a picture of your understanding of the structure of an
atom. What does it look like? What is inside of it? Express
what you know using a well-labeled diagram.
2. The charged parts of the atom are the _________________ and the ____________________. The
__________________ are positively charged and the __________________ are negatively charged.
The _____________________ are not charged and thus will not be of importance in this unit.
Structure of the Atom
3. An electrically neutral atom is an atom which _____.
a. does not have any protons or electrons
b. has more neutrons than the sum of all its protons and electrons
c. has a balance of protons and electrons (the same number of each)
d. has a balance of neutrons and electrons (the same number of each)
e. has a balance of protons, electrons and neutrons (the same number of each)
4. An electrically charged atom (sometimes referred to as an ion) can be distinguished from an
electrically neutral atom in that the charged atom (ion) _______.
a. does not have any neutrons
b. has lost one or more of its neutrons
c. either has a proton or an electron present somewhere within it
d. has a different number of neutrons than the sum of its electrons and protons
e. has an imbalance of protons and electrons (unequal numbers of these)
Physics Fact:
Protons (and neutrons) are located in the interior of an atom - in the nucleus. They are tightly bound and
unable to leave the atom except through nuclear processes. On the other hand, electrons are on the
exterior of an atom. They are exposed to other atoms and to forces which are capable of ejecting them or
stripping them of the atom.
5. The diagram depicts the eight electrons and eight protons in an oxygen atom.
a. Explain what must happen in order for an oxygen atom to become negatively
charged.
b. Explain what must happen in order for an oxygen atom to become positively
charged.
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
6. What is true of atoms in terms of being neutral, negatively charged, and positively charged is also
true of objects. An object which is negatively charged must have _____________________ (more,
less, the same number of) electrons compared to its protons. An object which is positively charged
must have _____________________ (more, less, the same number of) electrons compared to its
protons. An object which is electrically neutral must have _____________________ (more, less, the
same number of) electrons compared to its protons.
Summarize these verbal statements by inserting >, < or = symbols into the blanks below:
Negatively Charged
Positively Charged
Electrically Neutral
# of e- _____ # of p+
# of e- _____ # of p+
# of e- _____ # of p+
7. An object becomes charged due to an excess or deficiency (shortage) of electrons. Knowing the
exact number of excess or deficient electrons in an object allows one to determine the object's
charge. The charge of one electron is 1.6x10-19 C. Use this to determine the charge of the following
objects.
8. During a physics lab, a plastic strip was rubbed with cotton and became positively charged. The
correct explanation for why the plastic strip becomes positively charged is that ...
a. the plastic strip acquired extra protons from the cotton.
b. the plastic strip acquired extra protons from the charging process.
c. protons were created as the result of the charging process.
d. the plastic strip lost electrons to the cotton during the charging process.
9. Miss Chiff, the seventh-grade science teacher, greets her students in an unusual manner. She stands
at the door of her classroom, scuffing her feet back and forth on the carpet. As she does so, electrons
move from the carpet to her shoes to her body. Miss Chiff is now charged with a ________________
(positive, negative) type of charge. Then, Miss Chiff reaches out and touches her students on the
nose as they enter the classroom. As she does, some electrons leave Miss Chiff and move onto her
students. Miss Chiff is now _________ (more, less) negatively charged than before the contact with
the student. And the student is now charged with a _________________ (positive, negative) type of
charge.
10. In a lab report during the Static Electricity unit, Aaron Agin suggests that a sample of wool became
positively charged by gaining protons from the rubber balloon which it rubbed. Explain what is wrong
with Aaron's statement.
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Elementary Charge - Show all work!
1. An electrically neutral glass rod is rubbed against a neutral piece of silk. 2 x 1015 electrons are
transferred from the rod to the silk
a. How much charge in coulombs does this number of electrons represent? [Be sure to include
whether the charge is negative or positive] [-3.2 x 10-4 C]
b. At the end of this process, what type of charge does the glass rod have?
____________________
2. Determine the number of elementary charges present in:
a. 1.0 coulombs of charge [6.25 x 1018 e]
b. 4.5 x 10-10 coulombs of charge [2.8 x 109 e]
3. Determine the number of coulombs of charge present in: [include the sign of the charge]
a. 1.60 x 1019 protons [+2.56 C]
b. 4.0 x 105 neutrons [0 C]
c. 4.8 x 1024 electrons [-7.68 x 105 C]
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Show work
1. Which magnitude of charge could not be found on an object?
(1) -0.8 x 10-19 C
(2) -1.6 x 10-17 C
(3) +1.6 x 10-19 C
(4) +3.2 x 10-17 C
______________________________________________________________
2. A charge of 100 elementary charges is equivalent to
(1) 1.6 x 10-21 C
(2) 1.6 x 10-17 C
(3) 6.25 x 1016 C
(4) 6.25 x 1020 C
______________________________________________________________
3. An object gains 10 electrons. The charge on the object is:
(1) +10 elementary charge
(2) +1.6 x 10-18 C
(3) -10 elementary charge
(4) -1.6 x 10-20 C
______________________________________________________________
4. A metal sphere having an excess of +5 elementary charges has a net electric charge of
(1) 1.6 x 10-19 C
(2) 8.0 x 10-19 C
(3) 5.0 x 100 C
(4) 3.2 x 1019 C
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Charge Interactions
1. Review: Fill in the following blanks with the words electrons or protons. ____________________
are negatively charged and ____________________ are positively charged. As an object begins to
gain or lose electrons from its atoms, it becomes positively or negatively charged. A negatively
charged object has more ____________________ than ____________________ . A positively
charged object has more ____________________ than ____________________ .
2. Charged objects interact with one another. One can observe the interactions and infer information
about the type of charge present on an object. Complete the following statements to illustrate your
understanding of the three types of charge interactions:
a. Oppositely-charged objects ____________________________________________
b. Like-charged objects _________________________________________________
c. A charged object and a neutral object will _________________________________
3. Your physics teacher has prepared the room for the class's entry by suspending several inflated
balloons from the ceiling. Upon entering the physics room, you observe two balloons being drawn
towards each other as shown at the right. The attraction of these balloons for one another provides
evidence that ______.
a. both balloons are charged with the same type of charge
b. both balloons are charged with the opposite type of charge
c. both balloons are charged - either with the same type or opposite type of charge
d. only one of the balloons is charged; the other is neutral
e. at least one of the balloons is charged; the other is either charged or neutral
4. As you look around the room, you observe two other balloons being pushed away from each other.
The repulsion of these balloons from one another provides evidence that ______.
a. both balloons are charged with the same type of charge
b. both balloons are charged with the opposite type of charge
c. both balloons are charged - either with the same type or opposite type of charge
d. only one of the balloons is charged; the other is neutral
e. at least one of the balloons is charged; the other is either charged or neutral
5. In one part of the room, there are two balloons - one hanging straight down and the other being
attracted to it. This is evidence that _____.
a. balloon A is charged and balloon B is neutral
b. balloon B is charged and balloon A is neutral
c. balloon A is neutral and balloon B is negative
d. balloon A is neutral and balloon B is positive
e. … nonsense! This would never happen if the balloons are identical and simply suspended by
strings. They will attract each other and both be deflected from a vertical orientation.
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
6. Ana Litical is performing a physics lab in which she charges a variety of materials and tests to
determine their charge by bringing them near a negatively charged balloon and near some neutral
paper bits at rest on the table. Help Ana draw conclusions from her observations by entering +, -,
neutral (or a combination of these if absolute conclusiveness is not possible).
a. Object A is observed to attract the paper bits; object A must be ________________.
b. Object B is observed to attract the balloon; object B must be ________________.
c. Object C is observed to repel the balloon; object C must be ________________.
d. Object D is observed to attract both the paper bits and the balloon; object D must be
________________.
e. Object E is observed to attract the paper bits and repel the balloon; object E must be
________________.
7. On three occasions, the following charge interactions between balloons A, B and C are observed. In
each case, it is known that balloon B is charged negatively. Based on these observations, what can
you conclusively confirm about the charge on balloon A and C for each situation.
8. Jean Yuss is investigating the charge on several objects and makes the following findings.
Object C
attracts B
Object D
repels C
Object E
attracts D
repels F
Object F
attracts A
Jean knows that object A is negatively charged and object B is electrically neutral. What can Jean Yuss
definitively conclude about the charge on objects C, D, E, and F? Explain.
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Charging by Friction
Review:
1. Fill in the following blanks with the words electrons or protons. ____________________ are
negatively charged and ____________________ are positively charged. The
____________________ reside in the nucleus of atoms and are tightly bound; they will never leave
an atom as a result of electrostatic procedures. On the other hand, ____________________ are
located outside the nucleus and are easily removed from or added to atoms. As an object begins to
gain or lose ____________________ from its atoms, it becomes positively or negatively charged. A
negatively charged object has more ___________________ than ___________________. A
positively charged object has more __________________ than __________________.
2. During a physics lab, a plastic strip was rubbed with cotton and became positively charged. The
correct explanation for why the plastic strip becomes positively charged is that ...
a. the plastic strip acquired extra protons from the cotton.
b. the plastic strip acquired extra protons from the charging process.
c. protons were created as the result of the charging process.
d. the plastic strip lost electrons to the cotton during the charging process.
3. Objects differ from one another in terms of their relative tendency
to draw electrons towards themselves. Some materials are more
electron-greedy than others. A triboelectric series is a listing of a
variety of materials in order of their relative attraction for the electrons
of another material. The listing at the right is an example of a
triboelectric series. Materials listed near the top of the table have a
stronger affinity for electrons than those located below them. When
two materials are rubbed together, electrons are transferred from the
material which has the lesser affinity for electrons to the material
which has the greater affinity for electrons. The object which gains the
electrons acquires a ___________________ (+ or -) charge and the
object which loses the electrons acquires a ___________________
(+ or -). Use the triboelectric series to answer the following questions:
Triboelectric Series
Celluloid
Sulfur
Rubber
Copper, Brass
Amber
Wood
Cotton
Human Skin
Silk
Cat Fur
Wool
Glass
Rabbit Fur
4. When you pull a cotton sweater off your skin, electrons are transferred from the
___________________ (cotton, skin) to the __________________ (cotton, skin). As a result, your
body acquires a ___________ (+ , -) charge and the cotton sweater acquires a ___________ (+ , -)
charge.
5. When you rub a glass rod with a silk cloth, electrons are transferred from the __________________
to the __________________ . As a result, the glass rod acquires a ___________ (+ , -) charge and
the silk cloth acquires a ___________ (+ , -) charge.
6. Suppose you rub a rubber rod with a silk cloth and a second rubber rod with a wool sweater. The silk
cloth will acquire a __________ (+ , -) charge; the wool sweater will acquire a __________ (+ , -)
charge. The sweater and the cloth will then be observed to ______________________ (attract, repel,
not interact with) each other.
7. Suppose you rub a glass rod with a silk cloth and a second glass rod with rabbit fur. The silk cloth will
acquire a __________ (+ , -) charge; the rabbit fur will acquire a __________ (+ , -) charge. The
rabbit fur and the silk cloth will then be observed to ______________________ (attract, repel, not
interact with) each other.
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
8. Consider the statements below. Identify them as being either True or False.
a. When two objects made of different materials are rubbed together, they each acquire a charge.
b. When two objects made of different materials are rubbed together, they will either be both
charged positively or both charged negatively.
c. When two objects made of different materials are rubbed together, they will attract each other
after the charging process.
d. When two objects made of different materials are rubbed together, one object gains electrons and
the other objects gains protons.
e. When two objects made of different materials are rubbed together, the total amount of charge
among the two objects remains unchanged.
9. Saran Wrap has a larger electron affinity than Nylon. If Nylon is rubbed against Saran Wrap, which
would end up with the excess negative charge? ____________ Explain.
10. Object A is rubbed with object B. Object C is rubbed with object D. Objects A and D are observed to
repel each other. Object B is observed to repel a negatively charged balloon. This is conclusive
evidence that …
… object A acquired a __________ (+ , -) charge.
… object B acquired a __________ (+ , -) charge.
… object C acquired a __________ (+ , -) charge.
… object D acquired a __________ (+ , -) charge.
11. A teacher rubs a glass object and a felt cloth together and the glass becomes positively charged.
Which of the following statements are true? Circle all that apply.
a. The glass gained protons during the rubbing process.
b. The felt became charged negatively during this rubbing process.
c. Charge is created during the rubbing process; it is grabbed by the more charge-hungry object.
d. If the glass acquired a charge of +5 units, then the felt acquires a charge of -5 units.
e. This event violates the law of conservation of charge.
f. Electrons are transferred from glass to felt; protons are transferred from felt to glass.
g. Once charged in this manner, the glass object and the felt cloth should attract each other.
h. In general, glass materials must have a greater affinity for electrons than felt materials.
12. Balloons A and B are suspended from the ceiling by light threads; each balloon is made of rubber.
Balloon A was rubbed with animal fur. Balloon B was rubbed with animal fur. If a negatively charged
plastic tube is inserted between the two balloons, then one would observe that the two balloons
_____. (Refer to the triboelectric series.)
a. would deflect even more from a vertical orientation
b. would relax to a more vertical orientation
c. would not be effected at all by the presence of the plastic tube.
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Insulators, Conductors and Polarization
1. Insulators are different than conductors in that insulators ____.
a. do not contain electrons or protons
b. do not contain any charge
c. have a weaker affinity for electrons
d. do not allow charge to freely move
2. Materials through which electrons can move readily are classified as _____.
a. conductors
b. insulators
c. semi-conductors
3. A metal sphere attached to the top of an insulating stand. The metal sphere contains an excess of
electrons and is thus charged. A student holds various objects in her hand and touches the object to
the sphere. Which of the following objects below would cause sparks when the student touches the
object to the sphere?
a. a plastic straw
b. a piece of paper
c. a steel house key
d. a metal paper clip
e. a strip of aluminum foil
4. Consider these two spheres. They have both been charged. In one case the charge is isolated in
three distinct locations; in the other case, the excess charge is even distributed about the surface of
the sphere. Which one of these spheres is made of an insulating material and which is made of a
conducting material? Label which is which and support your answer with an explanation.
5. TRUE or FALSE:
Conductors cannot be charged by frictional rubbing. Explain your answer.
6. A balloon is charged by rubbing it with animal fur. It is then pressed against a wooden cabinet. The
balloon and cabinet attract, seeming to defy the force of gravity. This attraction is best explained by
____.
a. induction charging of the wood
b. frictional charging of the wood
c. polarization of wood molecules
d. polarization of balloon molecules
7. The above effect (in question #6) is most often noticed of ____.
a. conductors
b. insulators
c. charged objects
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
8. A negatively charged balloon is brought near a neutral conducting sphere. The presence of the
charged balloon will cause something to happen in the sphere. Which of the following would you
expect to occur? Select all that apply.
a. Electrons in the sphere will move to the balloon.
b. Protons in the sphere will move to the balloon.
c. Electrons in the sphere will move to the left side.
d. Electrons in the sphere will move to the right side.
e. Protons in the sphere will move to the left side.
f. Protons in the sphere will move to the right side.
9. The process of inducing the movement of charge within the sphere (referring to question #8) causes
positive and negative charge to be separated. This is known as ____.
a. grounding
b. charging
c. polarization
d. induction
10. Charged rubber rods are placed near a neutral conducting sphere, causing a redistribution of charge
on the spheres. Which of the diagrams below depict the proper distribution of charge on the spheres?
List all that apply.
11. In the above situation (question #10), the conducting sphere is ____. List all that apply.
a. charged
b. polarized
c. uncharged (neutral)
12. A physics teacher fills a burette with water and opens the valve, producing a steady stream of water
falling vertically to the sink. Then the teacher rubs a rubber balloon with animal fur and holds it near
the stream. The stream is observed to be deflected from its usual vertical flow towards the balloon.
Explain what is causing the deflection of the water stream.
13. A physics teacher charges a balloon negatively by
rubbing it with animal fur. The balloon is then placed
next to a wooden cabinet and adheres to the cabinet.
Explain what is happening at the particle level to cause
such a gravity-defying phenomenon. Add to the blowup
view of the diagram to assist in your explanation.
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Charging by Conduction and Grounding
Review:
1. Fill in the following blanks with the words electrons or protons. ____________________ are
negatively charged and ____________________ are positively charged. The
____________________ reside in the nucleus of atoms and are tightly bound; they will never leave
an atom as a result of electrostatic procedures. On the other hand, ____________________ are
located outside the nucleus and are easily removed from or added to atoms. As an object begins to
gain or lose ____________________ from its atoms, it becomes positively or negatively charged. A
negatively charged object has more ___________________ than ___________________. A
positively charged object has more __________________ than __________________.
2. A metal sphere is resting upon an insulating stand. A teacher holds a metal bar (with an insulating
handle). The teacher uses the metal bar to charge the metal sphere by conduction. Which one of the
processes describes what the teacher likely did to charge the sphere by conduction?
a. The teacher rubbed the bar and the sphere together.
b. The teacher held the bar near the sphere and then touched the sphere with her hand.
c. The teacher charged the bar and then contacted it to the sphere.
Consider the conduction charging process described below:
1. A teacher holds a negatively charged metal bar by its insulating handle and touches it to a metal
sphere (attached to an insulating stand).
2. The teacher pulls the metal bar away and the metal sphere acquires a charge.
3. The excess negative charge spreads uniformly about the surface of the metal sphere.
3. Diagram A is the charging step. How does the sphere become charged?
a. Electrons move from the insulating stand into the sphere.
b. Electrons move from the charged metal bar into the sphere.
c. Protons move from the sphere into the negatively charged bar.
4. When the metal bar is pulled away in Diagram B, the metal bar is _____.
a. positively charged
b. electrically neutral
c. still negatively charged, but has fewer excess electrons than it previously did.
5. Diagram C shows the excess negative charge distributed differently than it is in Diagram B. Explain
why the excess negative charge would distribute itself as it does in Diagram C.
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Now consider the conduction charging of the sphere using a positively charged metal bar:
A. A teacher holds a positively charged metal bar by its insulating handle and touches it to a metal
sphere (attached to an insulating stand).
B. The teacher pulls the metal bar away and the metal sphere acquires a charge.
C. The excess positively charge spreads uniformly about the surface of the metal sphere.
6. Diagram A is the charging step. How does the sphere become charged?
a. Protons move from the insulating stand into the sphere.
b. Protons move from the charged metal bar into the sphere.
c. Electrons move from the sphere into the positively charged bar.
7. When the metal bar is pulled away in Diagram B, the metal bar is _____.
a. negatively charged
b. electrically neutral
c. still positively charged, but has fewer excess protons than it previously did.
Two different processes are shown in the diagrams below:
A.
B.
C.
D.
A negatively charged metal sphere is touched.
The hand is pulled away and the sphere is then electrically neutral.
A positively charged metal sphere is touched.
The hand is pulled away and the sphere is then electrically neutral.
8. The process of neutralizing the charged spheres as depicted above is known as _____.
a. charging
b. polarization
c. induction
d. grounding
9. When the negatively charged sphere is touched, ______ move from the _______ to the _______.
a. electrons, sphere, hand
c. protons, sphere, hand
b. electrons, hand, sphere
d. protons, hand, sphere
10. When the positively charged sphere is touched, ______ move from the _______ to the _______.
a. electrons, sphere, hand
b. electrons, hand, sphere
c. protons, sphere, hand
d. protons, hand, sphere
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Charging by Induction
Review:
1. Fill in the following blanks with the words electrons or protons. ____________________ are
negatively charged and ____________________ are positively charged. The
____________________ reside in the nucleus of atoms and are tightly bound; they will never leave
an atom as a result of electrostatic procedures. On the other hand, ____________________ are
located outside the nucleus and are easily removed from or added to atoms. As an object begins to
gain or lose ____________________ from its atoms, it becomes positively or negatively charged. A
negatively charged object has more ___________________ than ___________________. A
positively charged object has more __________________ than __________________.
Consider the following process:
A uncharged metal pop can is attached to a Styrofoam cup (which acts as an insulating stand). A
negatively charged balloon is brought near the pop can. While the balloon is held near, the can is
touched. When the can is pulled away, the pop can is charged.
2. This process is known as _____.
a. charging by conduction
c. polarization
b. charging by induction
d. grounding
3. When the balloon is held near to the pop can (and before being touched by the hand), the distribution
of charge on the pop can is best depicted by diagram _____.
4. When the pop can is touched by the hand, ______ move from the ______ to the _______.
a. protons, hand, can
b. protons, can, hand
c. electrons, hand, can
d. electrons, hand, can
5. This process causes the can to acquire a _____ charge.
a. negative
b. positive
c. neutral
6. When the induction charging process is complete, the balloon is _____.
a. positively charged
b. electrically neutral
c. still negatively charged, only having fewer excess electrons as before the process began
d. still negatively charged, having the same amount of negative charge as it previously had
7. In general, the use of a negatively charged object to charge another object by induction causes the
other object to acquire a _____ charge
a. positive
b. negative
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Now consider a similar process:
A uncharged metal pop can is attached to a Styrofoam cup (which acts as an insulating stand). A
negatively charged balloon is brought near the pop can. While the balloon is held near, the can is
touched. When the can is pulled away, the pop can is charged.
8. When the balloon is held near to the pop can (and before being touched by the hand), the distribution
of charge on the pop can is best depicted by diagram _____.
9. When the pop can is touched by the hand, ______ move from the ______ to the _______.
a. protons, hand, can
b. protons, can, hand
c. electrons, hand, can
d. electrons, hand, can
10. This process causes the can to acquire a _____ charge.
a. negative
b. positive
c. neutral
In the above induction charging processes, there are two basic steps; a polarization step and a
charging step. In the charging step, the hand serves as a ground - an object which serves as a
seemingly infinite source of or sink for electrons. During the charging step, electrons move into or out of
the ground (hand) in order to charge the pop can. Another means of charging the pop can involves the
use of another conducting object. For instance, another pop can could be used. The diagrams below
depict the induction charging process using a second pop can in place of the hand.
11. In terms of electron movement, explain what is happening in Diagrams B and C above. Finally, state
the charge acquired by the left and the right can as a result of this process.
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Transfer of Charge - Show all work!
1. A piece of plastic PVC pipe is rubbed against a piece of fur. During this process the pipe gains electrons.
a. What charging process is used to transfer charges by touching objects together?
____________________________
b. After the pipe was rubbed on the fur, the pipe became _________________________ charged.
c. After the pipe was rubbed on the fur, the fur became _________________________ charged.
d. Which particles that make up atoms were transferred during this process? _____________________
e. Which particles that make up atoms were NOT transferred during this process?
____________________
f. Based on the Law of Conservation of Charge, what can we say about the amount of charge on the fur
and the pipe after the charging process?
2. Three identical, charges spheres are used for an experiment. Sphere A has a charge of -4.0 coulombs. Sphere B
has a charge of -8.0 coulombs. Sphere C has a charge of +9.0 coulombs.
STEP 1: Sphere A is touched to sphere B and then taken away while sphere C is kept isolated. What are
the charges on the three spheres after this occurs?
A __________ B ___________ C ___________ Total ____________
STEP 2: Spheres B and C are now brought into contact and separated, while sphere A is kept isolated.
What are the charges on the three spheres at this point?
A __________ B ___________ C ___________ Total _____________
STEP 3: All three spheres are now brought into contact with one another at the same time then
separated. What are the charges on the three spheres at this point?
A __________ B ___________ C ___________ Total ______________
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
3. A positively charged rod is brought near a neutral sphere as shown below.
a. Sketch the distribution of charge on the sphere while the positive rod is held nearby.
b. What is the process by which the charge on the sphere is redistributed called? ____________________
4. A negatively sphere is connected to the ground. The charge on the sphere is neutralized during this process.
Sketch the flow of charge that allows this neutralization to occur on the diagram above.
5. A positively charged sphere is connected to the ground. The charge on the sphere is neutralized during this
process.
Sketch the flow of charge that allows this neutralization to occur on the diagram above.
6. A negative rod is used to…
a. …charge a neutral object by conduction. What overall charge does the neutral object gain? ________
b. …polarize an object by induction. What overall charge does the object gain? __________
c. …charge a neutral object by induction. What overall charge does the neutral object gain? __________
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Coulomb's Law
Coulomb's Law can be states in equation form as
This equation can be used as an algebraic recipe for solving computational problems or as a guide to
thinking about how an alteration in the quantity of charge or the distance between charged objects effects
the amount of attractive or repulsive force.
Using Coulomb's Law as a "Guide to Thinking"
Alteration in the Quantity of Charge
1. Two charged objects have a repulsive force of .080 N. If the charge of one of the objects is doubled,
then what is the new force?
2. Two charged objects have a repulsive force of .080 N. If the charge of both of the objects is doubled,
then what is the new force?
Alteration in the Distance between Charged Objects
3. Two charged objects have a repulsive force of .080 N. If the distance separating the objects is
doubled, then what is the new force?
4. Two charged objects have a repulsive force of .080 N. If the distance separating the objects is tripled,
then what is the new force?
5. Two charged objects have an attractive force of .080 N. If the distance separating the objects is
quadrupled, then what is the new force?
6. Two charged objects have a repulsive force of .080 N. If the distance separating the objects is halved,
then what is the new force?
Alteration in both the Quantity of Charge and the Distance
7. Two charged objects have a repulsive force of .080 N. If the charge of one of the objects is doubled,
and the distance separating the objects is doubled, then what is the new force?
8. Two charged objects have a repulsive force of .080 N. If the charge of both of the objects is doubled
and the distance separating the objects is doubled, then what is the new force?
9. Two charged objects have an attractive force of .080 N. If the charge of one of the objects is
increased by a factor of four, and the distance separating the objects is doubled, then what is the new
force?
10. Two charged objects have an attractive force of .080 N. If the charge of one of the objects is tripled
and the distance separating the objects is tripled, then what is the new force?
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Using Coulomb's Law as an "Algebraic Recipe"
11. A balloon with a charge of 4.0 x 10-5 C is held a distance of 0.10 m from a second balloon having the
same charge. Calculate the magnitude of the repulsive force. PSYW
12. Calculate the electrical force (in Newtons) exerted between a 22-gram balloon with a charge of -2.6
μC and a wool sweater with a charge of +3.8 μC; the separation distance is 0.75 m. (NOTE: a μC or
microCoulomb is a unit of charge; 106 μC = 1 C) PSYW
13. Suppose that two equally charged spheres attract each other with a force of -0.492 N ("-" means
attractive) when placed a distance of 29.1 cm from each other. Determine the charge of the spheres.
PSYW
14. A +5.0 μC charge and a -6.0 μC charge experience an attractive force of -0.72 N ("-" means
attractive). Determine their separation distance. PSYW
15. A balloon has been rubbed with wool to give it a charge of -1.0 x 10-6 C. A plastic tube with a charge
of +4.0 x 10-6 C is held a distance of 0.50 m above the balloon. Determine the electrical force of
attraction between the tube and the balloon. PSYW
In the space at the left, construct a free-body diagram
showing the direction and the type of all forces acting
upon the 30.0-gram balloon.
Will the balloon accelerate up, down, or not at all?
_____________
If there is acceleration, then calculate its value. (Assume that the plastic tube is held a constant
distance of 0.5 m from the balloon.) PSYW
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Coulomb’s Law (Electrostatic Force)- Show all work!
1. Two objects, one with a charge of +2 x 10-6 coulombs and the other with a charge of -3 x 10-5
coulombs are placed so that they are separated by a distance of 0.035 meters.
a. Calculate the electrostatic force that the two objects exert on one another. [440 N]
b. If the distance between the two objects was increased to 0.070 meters, what would the new
electrostatic force between them be? [110 N]
2. Sketch a graph that relates the electrostatic force between two objects to the distance between
them.
3. Sphere A has an excess of 5 x 1016 electrons. Sphere B has an excess of 6 x 1017 electrons.
a. Determine the charge on each sphere in coulombs. [A = 0.008 C; B = 0.096 C]
b. Calculate the electrostatic force that sphere A exerts on sphere B when they are separated by a
distance of 2 x 103 meter. [1.7 N]
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
1. Two point charges attract each other with a force of 8.0 x 10-5 newtons. If the distance between the
charges is doubled, the force will become
(1) 16 x 10-5 N
(2) 2.0 x 10-5 N
(3) 64 x 10-5 N
(4) 4.0 x 10-5 N
______________________________________________________________
2. What is the magnitude of the electrostatic force exerted on sphere A?
(1) 1.1 x 10-9 N
(2) 1.3 x 10-8 N
(3) 120 N
(4) 10 N
______________________________________________________________
3. The electrostatic force of attraction between two small spheres that are 1.0 meter apart is F. If the
distance between the spheres is decreased to 0.5 meter, the electrostatic force will then be
(1) F/2
(2) 2F
(3) F/4
(4) 4F
______________________________________________________________
4. If the charge on each of two point sources is doubled, the electrostatic force between them
(1) remains the same
(2) is one-half as great
(3) is twice as great
(4) is four times as great
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Electric Field
1. The standard metric units of measurements for electric field strength are __________________.
2. The direction of the electric field vector is defined as __________________________________
____________________________________________________________________________.
Use the electric field equations to answer the following questions.
3. A test charge of +1x10-6 C experiences a force of 0.050 N. The electric field strength is _________.
4. A test charge of +1x10-6 C experiences a force of 0.10 N. The electric field strength is _________.
5. An object with a charge of Q creates an electric field. A positive test charge, q, is used to test the
strength of the field. If the charge of the test charge q is doubled, then it will experience ______ (2X,
4X, 1/2, 1/4-th, the same) force; the electric field strength at this location will be _______ (2X, 4X, 1/2,
1/4-th, the same as) the original value. If the distance between the charge and the test charge is
doubled, then the test charge will experience ______ (2X, 4X, 1/2, 1/4-th, the same) force; the electric
field strength at this location will be _______ (2X, 4X, 1/2, 1/4-th, the same as) the original value.
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Electric Field Lines
1. Electric field lines begin on ______ (+, -) charges or at infinity and terminate on _______ (-, +)
charges or infinity. The number of lines which emanate from a charge or approach a charge depends
upon. At locations where a line meets the surface of a charge, the lines are drawn in a
______________ (tangent, radial) direction. The strength of the electric field is _________________
(smallest, greatest) wherever the lines are closest together.
2. Use your understanding of electric field lines to identify the charges on the objects in the following
configurations.
3. Observe the electric field lines below for various configurations. Rank the objects according to which
have the greatest magnitude of electric charge, beginning with the smallest charge.
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Electric Fields - Show all work!
1. Sketch the electric field in each of the following cases.
2. A sphere with a +2.0 x 10-6 coulomb charge experiences a force of 4.0 x 10-4 newtons while situated in
a uniform electric field. Determine the strength of the electric in newtons per coulomb. [200 N/C]
3. An electron is placed between the two electrically charged plates shown below. The electron
accelerates toward the upper plate. The electric field strength between the plates is 4.8 x 10-11 newtons
per coulomb.
a. Label the plates with the correct charge.
b. Sketch at least four electric field lines to represent the field between the plates. Ensure that the
direction of the field lines is correct!
c. Use the electric field strength given above and the charge on the electron to determine the net force
acting on the electron while it is between the plates. [7.68 x 10-30 N]
d. Calculate the acceleration of the electron while it is between the plates. [8.43 m/s2]
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
1. The diagram below shows some of the lines of electrical force around a positive point charge. Point A
is nearest to the charge, point B is farther away, and point C is the farthest.
The electric field strength is
(1) greatest at point A
(2) greatest at point B
(3) greatest at point C
(4) equal at points A, B, and C
_____________________________________________________________
2. In the diagram below, A is near a negatively charged sphere. Which vector best represents the
direction of the electric field at point A?
_____________________________________________________________
3. As the electron that is placed between the plates below moves toward the positive plate, the force
acting on it…
(1) decreases
(2) increases
(3) remains the same
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
Electric Potential Difference
Review:
1. Electric field is defined as the aura about the space surrounding a charged object which exerts an
electrical influence upon other charged objects in that space. The direction of the electric field
vector is defined as the direction which a positive test charge would be accelerated. Potential
energy is the energy stored in an object due to the position of that object.
A Gravitational Analogy:
2. Two diagrams are shown at the right.
In diagram A, a mass is held at an elevated
position. When let go of, the mass falls from point
A to point B.
In diagram B, the mass is originally at point A and
a person moves it back up to point B. For each
diagram, indicate if work is done by a nonconservative force in moving the object from its
initial position (point A) to its position at point B.
Finally, indicate the position of greatest
gravitational potential energy.
Circle the answers in the space below the
diagrams.
5. The following diagrams show an electric field and two points - labeled A and B - located within the
electric field. A positive test charge is shown at point A. For each diagram, indicate whether work
must be done upon the charge to move it from point A to point B. Finally, indicate the point (A or B)
with the greatest electric potential energy and the greatest electric potential (PE/charge).
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
4. When work is done on a positive test charge to move it from one location to another, potential energy
_________ (increases, decreases) and electric potential _________ (increases, decreases). When a
positive test charge naturally moves from one location to another (without the exertion of a nonconservative force), potential energy _________ (increases, decreases) and electric potential
_________ (increases, decreases).
5. The diagram at the right shows a light bulb connected to a 12-V car battery. The + and - terminals are
shown.
a. As a + charge moves through the battery from D to A, it
________ (gains, loses) potential energy and ________ (gains,
loses) electric potential. The point of highest energy within a
battery is the ______ (+, - ) terminal.
b. As a + charge moves through the external circuit from A to D, it
________ (gains, loses) potential energy and ________ (gains,
loses) electric potential. The point of highest energy within the
external circuit is closest to the ______ ( +, - ) terminal.
c. Use >, <, and = signs to compare the electric potential (V) at
the four points of the circuit.
VA ______VB _______VC________ VD
6. The role of a battery in an electrical circuit can be described in three different ways. First, it is the
energy supply. Second, the energy supplied by the battery is required to do work upon the charge to
move it against the electric field from the negative terminal to the positive terminal. And third, by
moving the charge against the field from negative to positive terminal, the battery establishes an
electric potential difference across the two ends of the external circuit. Without a potential difference
between two locations, charge will not move. When there is an electric potential between two
locations, charge will move from the location of high potential to the location of low potential. The
mount of potential difference (V) between two locations is related to the work done in moving an
amount of charge (Q) from the low potential to the high potential location.

a. It takes _____ J of work to move 1 C of charge from the - to the + terminal of a 1.5-volt battery.
b. It takes _____ J of work to move 2 C of charge from the - to the + terminal of a 12-volt battery.
c. It takes 18 J of work to move _____ C of charge from the - to the + terminal of a 12-volt battery.
d. It takes 12 J of work to move 2 C of charge from the - to the + terminal of a _____-volt battery.
e. It takes _____ J of work to move _____ C of charge from the - to the + terminal of a 12-volt
battery.
7. In the battery, energy is supplied to the charge to move it from
low potential (- terminal) to high potential (+ terminal). Once at
the + terminal, the charge spontaneously moves through the
external circuit, losing energy as it passes through each electrical
device. The electric potential which is gained by the charge when
it passes through the battery is lost by the charge as it moves
through the external circuit. These gains and losses in electric
potential are often represented using an electric potential diagram.
For the circuit at the right, complete the electric potential
diagram, showing the relative potential of locations A, B, C, D, E,
and F.
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Electrical Potential - Show all work!
1. Convert 3.5 x 10-16 joules to electron-volts. [2187.5 eV]
2. 4 x 10-8 joules of work are done in moving a charge of 2 x 10-6 coulombs.
a. Since work had to be done to move the charge, what form of energy is increasing?
_________________
b. How much electrical potential is generated during this process? [0.02 V]
3. A 0.005 kilogram object with a charge of 2 x 10-5 coulombs is positioned in an electric field so that it
has an electrical potential of 1.5 volts. The charged body is released so that it is free to move.
a. How much kinetic energy will the object gain after it is released? [3.0 x 10-5 J]
b. What maximum velocity will this object reach? [0.11 m/s]
4. An object with an excess of 5 electrons is accelerated through an electric field so that it loses 15 volts
of electrical potential.
a. How much kinetic energy (in eV) does this object gain during this process? [75 eV]
b. Convert this energy into joules [1.2 x 10-17 J]
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REGENTS PHYSICS – STATIC ELECTRICITY – PRACTICE NAME __________________
1. 24 joules of work are done in moving 2 coulombs of charge a distance of 3 meters in an electric field.
What is the potential difference through which the charge is moved?
(1) 48 V
(3) 12 V
(2) 16 V
(4) 4.0 V
______________________________________________________________
2. Two metal plates are charged so that the electrical potential in the field between them is 100 volts.
How much energy is needed to move 1 coulomb of negative charge from the positive to the negative
plate?
(1) 1 J
(3) 1 eV
(2) 100 J
(4) 100 eV
______________________________________________________________
3. The work required to move a charge of 3.0 coulombs through a potential difference of 12 volts is
(1) 0.25 J
(3) 36 J
(2) 9 J
(4) 4.0 J
______________________________________________________________
4. How much work is required to move a single electron through a potential difference of 100 volts?
(1) 1 eV
(3) 1.6 x 10-17 J
(2) 10 eV
(4) 1.6 x 10-19 J
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