Name _______________________________________ Date ________________ Period _____________
Electric Charges
Section 1:
1) What force exists between an uncharged object and a charged object?
Choose between attractive, repulsive and no force.
2) What are the charged sub-atomic particles and where are they in an atom?
3) What do we mean when we say that something is neutral?
4) What do we mean when we say that something has a negative charge?
5) What do we mean when we say that something has a positive charge?
6) How do things get charged by rubbing?
7) Which type of charged sub-atomic particles can easily leave an atom or easily be gained by an atom?
8)
What sub-atomic particles are moving in wires when we use electricity?
9)
Distinguish between a conductor and an insulator.
10) What is the interaction between a positively charged object and a positively charged object?
11) What is the interaction between a negatively charged object and a positively charged object?
12) What is the interaction between a negatively charged object and a negatively charged object?
13) Summarize the answers from the past 3 questions: Like charges ___________ and unlike charges
______________.
14) Summarize Coulomb’s law:
a) The bigger the charges, the_____________ the electrostatic force.
b) The greater the distance between charges, the ___________ the electrostatic force.
Section 2:
15) Electrostatic precipitators are used to clean some of the smoke and pollutant particles from the exhaust
from coal burning power plants. An electrostatic precipitator uses a charged object to attract charged
smoke particles and pull them out of exhaust, so they don’t pollute. If the charged object is negative,
what type of charge is on the smoke particles?
16) Sometimes metal objects are painted by using the principles of electrostatics. The paint is given a charge
and the metal object to be painted is also charged. When the metal object is a rail, sometimes the paint
particles will even fly over to the other side of the rail and stick, giving the rail an even coating even when
the paint is only sprayed from one side. If the paint molecules have a positive charge, what must be the
charge on the rail?
17) When socks cling to a shirt that is being taken from the dryer, you can conclude that: (choose one)
a. The socks and the shirt have the same charge.
b. The socks and the shirt have opposite charges.
c. Either the socks or shirt is charged and the other item is neutral.
d. EITHER ANSWER b or c IS CORRECT
18) A student charges two small balloons and hangs them by a string. They push away from each other like
this:
a) What causes them to push away?
b) She reads in a physics book that a charged balloon will have a negative charge. This means
that: (choose one)
i)
The balloon has more protons than electrons
ii)
The balloon has an equal number of protons and electrons
iii)
The balloon has more electrons than protons
iv)
We cannot tell the relative numbers of protons and electrons
c) A charged piece of tape is brought toward one of the charged balloons. It is attracted to the
balloon. What is the charge on the tape?
d) If the charge on one or both of the balloons were somehow increased, what would happen to
the strength of the repulsive force on the balloons?
e)
If the distance between the balloons was increased, what would happen to the strength of the
repulsive force on the balloons?
Section 3:
19) Coulomb’s Law looks a lot like the law of Universal Gravitation. Compare the relative sizes of the
gravitational constant, G and the Coulomb’s law constant, k. What does this tell us about the relative
strengths of the gravitational force and the electrostatic force?
20) How many Coulomb’s are in one microcoulomb? 1μC = ______________ C
21) You have a charge of +1 μC and another of charge -5 μC. They are separated by a distance of 0.3 m. If
the force on the +1 μC charge due to the other is 0.5 Newtons TOWARD the negative charge, what is the
magnitude and direction of the force on the -5 μC charge?
22) Your initial situation is one negative charge and one positive charge. Say what would happen to the force
that one charge exerts on the other with each of the following changes. Start from the original situation
each time.
a. You triple the distance between the charges:
b.
The magnitude of charge on just one object is cut in half.
c. The magnitude of charge on both objects is cut in half.
d. The magnitude of charge on both objects is cut to ¼ of what it was?
e. The magnitude of charge on both objects is tripled.
f.
The magnitude of charge on both objects is cut in half and the distance between the charges is
also cut in half.
g. The magnitude of charge on one object is tripled and the distance between the charges is also
tripled.
h. The magnitude of one charge is tripled and the magnitude of the other is quadrupled.
i.
The distance between the charges is cut to 1/5 of what it originally was.
j.
The magnitude of one charge is doubled and the magnitude of the other is cut into ¼ of what it
was. The distance between the charges is quadrupled.
k. The magnitude of one charge is cut in half. The distance between the charges is also cut in half.
23) You have two identical positive charges separated by a distance of 0.25 meters. If the positive charge on
one of the objects is doubled, what happens to the force on one charge due to the other?
24) You have two identical positive charges separated by a distance of 0.25 meters. If the positive charge on
BOTH of the objects is doubled, what happens to the force on one charge due to the other?
25) You have two identical positive charges separated by a distance of 0.25 meters. If the distance between
the objects is doubled what happens to the force on one charge due to the other?
26) You have two identical positive charges separated by a distance of 0.25 meters. If the objects are brought
to a separation of 1/3 of their previous separation, what happens to the force on one charge due to the
other?
27) You have two small charged objects. One has a charge of + 10 μC and the other has a charge of + 3 μC.
They are separated by a distance of 1.1 meters. The electrostatic force on the + 10 μC charge due to the
other is 0.22 N AWAY from the other charge. What are the magnitude and direction of the force on the
+3 μC charge?