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General Physics 2
Learning Activity Sheets
Quarter 3 - Week 1: Electrical Charges & Columb’s Law
First Edition, 2021
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Development Team of the Learner’s Activity Sheets
Writer:
Editors:
AR A. Ranesis
Ric Me D. Diaz
Shekaina Faith C. Lozada
Edna E. Trinidad
Relyn D. Raza
Glenn Pacot
Airene Jane B. Pelegro
Ace Michael B. Magalso
Layout Reviewers:
Ric Me D. Diaz
Shekaina Faith C. Lozada
Marvin T. Tejano
Management Team:
Josita B. Carmen, Schools Division Superintendent
Jasmin R. Lacuna, Asst. Schools Division Superintendent
Celsa A. Casa, CID Chief
Bryan L. Arreo, LR Manager
Edna E. Trinidad, Science Education Program Supervisor
Kevin Hope Z. Salvaña, Regional Science Coordinator
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
WEEKLY LEARNING ACTIVITY SHEETS
General Physics 2, Grade 12, Quarter 3, Week 1
ELECTRICAL CHARGES & COULOMB’S LAW
Name: _________________________________________
Section: __________________
Learning Objectives:
After the lesson, the students will be able to:
1. describe using a diagram charging by rubbing and charging by induction
(STEM_GP12EMIIIa-1);
2. explain the role of electron transfer in electrostatic charging by rubbing
(STEM_GP12EMIIIa-2);
3. describe experiments to show electrostatic charging by induction
(STEM_GP12EMIIIa-3);
4. calculate the net electric force on a point charge exerted by a system of point charges
(STEM_GP12EMIIIa-6);
5. describe an electric field as a region in which an electric charge experiences a force
(STEM_GP12EMIIIa-7); and
6. calculate the electric field due to a system of point charges using Coulomb’s law and
the Superposition Principle (STEM_GP12EMIIIa-10).
Key Concepts








Positive and negative charges are the two types of electrical charges.
Electrons are the negative charges and protons are the positive ones.
Unlike charges attract each other while same charges repel.
Losing or gaining electron means charging.
Matter is charged in three ways namely charging by friction, charging by contact,
and charging by induction.
A material rubs to another one is charged by friction. The material that loses
electron and the other material that gains electron are both charged. The number
of lost and gained electrons are adequate to one another.
A neutral sphere can be charged by contact or conduction if a negatively
charged material passes electrons by touching a neutral sphere.
If an object induces charge with other object without contact, it is called charging
by induction.
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
1
n
Fig.1. Charging by friction
Source:https://d3jlfsfsyc6yvi.cloudfront.net/image/mw:1024/q:85/https%3A%2F%2Fhaygot.s3.a
mazonaws.com%3A443%2Fcheatsheet%2F10810_689d8cf6d6a441078f18c202840a6a5a.jpg
Fig. 2. Charging by conduction
Source:https://www.physicsclassroom.com/Class/estatics/u8l2c1.gif
Fig. 3. Charging by induction
Source:https://www.physicsclassroom.com/Class/estatics/u8l2b2.gif
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
2






Electrical conductors are materials or substances which have free electrons. Free
electrons can move freely throughout these materials. A small region of a good
conductor when charged can distribute itself over an entire surface area.
Examples of good conductors are copper, silver and iron.
Electrical insulators are materials or substances in which all of its electrons are
bound to atoms or don’t have free electrons. The movements of free electrons in
insulators are opposite to conductors. A small region of a good insulator when
charged cannot move to other regions. Examples of good insulators are rubber,
plastic and wood.
Semiconductors’ properties are in between those of insulators and conductors.
Examples of semiconductor materials are silicon and tellurium which are
commonly used in making electronic chips.
An electric field is a region or space where a charged particle experiences an
electrical force without contact. The charged particle will accelerate to the
direction where there is an unbalanced force if it is free to move.
The electric field can be represented by drawing a series of lines going from a
positive charge to a negative charge, or to or from infinity if only one charge is
present.
The strength of electric field depends on the distance between the electric fields.
The closer they are, the stronger while the farther they are, the weaker.
Fig. 4. Electrical field line pattern of positive charge (left) and negative charge (right)
Source:https://isaacphysics.org/api/v2.15.1/api/images/content/concepts/physics/figures/electric_fi
eld_e_field_point_capacitor_2.svghttps://www.physicsclassroom.com/Class/estatics/u8l2b2.gif
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
3
Fig. 5. Different electrical field density lines
Source:https://www.physicsclassroom.com/Class/estatics/u8l4c3.gif
Fig. 6. Electrical field line patterns of same electrical charges (left) and opposite charges (right)
Source:https://www.physicsclassroom.com/Class/estatics/u8l4c8.gif

Coulomb's law states that the magnitude of the electric force between two-point
charges is directly proportional to the product of the charges and inversely
proportional to the square of the distance between them (Young and Freedman,
2012).
F k
q1q2
r2
where
N  m2
k  8.9876  10
C2
9
where q1 represents the quantity of charge on object 1 (in Coulombs), q2
represents the quantity of charge on object 2 (in Coulombs), and r represents the
distance of separation between the two objects (in meters). The symbol k is a
proportionality constant known as the Coulomb's law constant.
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
4

If the charges q1 and q2 are of the same sign (both positive or both negative) then
the force is mutually repulsive and the force on each charge points away from the
other charge. If the charges are of opposite signs (one positive, one negative) then
the force is mutually attractive and the force on each charge points toward the
other one.
Fig.7. Unlike charges attract each other while same charges repel
Source:http://hyperphysics.phy-astr.gsu.edu/hbase/electric/imgele/coulaw.png
Sample problems:
1. A point charge of +3.00 × 10−6 C is 12.0 cm distant from a second point charge
of −1.50 × 10−6 C. Calculate the magnitude of the force on each charge.
Solution:
F k
q1q2
r2


2
6
6

9 N  m  3.00  10 C 1.5  10 C

  8.99  10
2
2
C
12.0  10  2 m





= 2.81 N
Each charge experiences a force of attraction of magnitude 2.81 N.
2. What must be the distance between point charge q1 = 26.0 μC and point charge
q2 = −47.0 μC for the electrostatic force between them to have a magnitude of
5.70 N?
Solution:
We are given the charges and the magnitude of the (attractive) force between
them. We can use Coulomb’s law to solve for r, the distance between the charges:
F k
q1q2
r
2

r2  k
q1q2
Plug in the given values:
F



2
6
6

9 N  m  26.0 10 C 47.0 10 C

r   8.99 10
 1.93m 2
2
5.70 N 
C 

2
This gives: r  1.93m 2  1.39m
The distance between the charges is 1.39 m.
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
5


Principle of Superposition states that when a number of charges are interacting,
the total force on a given charge is the vector sum of forces exerted on it by all
other charges. This principle makes use of the fact that the forces with which two
charges attract or repel one another are not affected by the presence of other
charges.
The electric force, like all other forces, is a vector quantity. Hence, the force
experienced by a charge due to two or more charges is the vector sum of all the
forces.




Fnet  F1  F2  F3 ...
The X and Y components of the net force are








F net , x  F1, x  F 2, x  F 3, x  ...
F net , y  F1, y  F 2, y  F 3, y  ...
The magnitude and direction of the net force are
Fnet  Fnet2 , x  Fnet2 , y
F 
  tan 1  net , y 
 Fnet , x 
Sample problem:
Three different, small charged objects are placed as shown in Figure 8. The
charges q1 and q3 are fixed in place; q2 is free to move. Given q1 = 2e, q2 = −3e ,
and q3 = −5e , and that r = 2.0 × 10−7 m , what is the net force and direction on
the middle charge q2? Note: e = 1.602 × 10−19 C
Solution:
1. Find the net force on q2



F2  F21  F23
r
A. Find the magnitude of F23
Fx   F23  k
q1q2
r2


2
19

C 8.0110 19 C
9 N  m  4.806  10

  8.99 10
2
2
C
4.00 107 m


 2.16 10 14 N

B. Find the magnitude of F21
Fy  F21  k
q1q2
r2
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
6


2r
Fig.8
Source:https://files.mtstatic.com/s
ite_4539/11854/


2
19

C 3.204 10 19 C
9 N  m  4.806  10


  8.99 10
2
C 2 
2.00 107 m

 3.46 10 14 N



C. Calculate the two orthogonal components of F23 and F21
F23,x = F23 cos 0° = (-2.16 × 10-14 N) (1) = -2.16 × 10-14 N
F23,y = F23 sin 0° = (-2.16 × 10-14 N) (0) = 0
F21,x = F21 cos 90° = (3.46 × 10-14 N) (0) = 0
F21,y = F21 sin 90° = (3.46 × 10-14 N) (1) = 3.46 × 10-14 N
D. Calculate the net force, F2
Fx = F23,x + F21,x = -2.16 × 10-14 N + 0 = -2.16 × 10-14 N
Fy = F23,y + F21,y = 0 + 3.46 × 10-14 N = 3.46 × 10-14 N
F  Fx2  Fy2

 2.16 10
14
 
2
N  3.46  10 14 N

2
 4.08 10 14 N
2. Find the direction
F 
  tan 1  net , y 
 Fnet , x 
 3.46 10 14 N 

  tan 
14

2
.
16

10
N


 58
1
The net force and the direction on the middle charge q2 is 4.08 × 10-14 N, -58°.
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
7
Activity 1. Rub It!
Objective
The learners should be able to explain the role of electron transfer in electrostatic
charging by rubbing
What you need:
 Cloth (silk or cotton)
 Plastic comb
 Dry paper
What to do:
1. Cut a piece of dry paper into a few quarter-inch squares.
2. Vigorously rub the plastic comb against the piece of cloth.
3. Put the plastic comb near the pieces of paper.
4. Record the behavior of the paper squares.
Guide Questions:
1. What have you observed to the paper squares after the plastic comb is rubbed
against a piece of cloth?
2. Why the paper squares behaved like that?
3
Practical application
is scientifically
explained consistent
to the concepts, and
has no
misconceptions.
Rubric for Guide Questions 1 and 2
2
1
Practical application Practical application
is scientifically
is explained
explained consistent consistent to the
to the concepts, but concepts but with
with minimal
misconceptions.
misconceptions.
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
8
0
No discussion.
Activity 2. Induction, Conduction
Objectives
The learners should be able to:
1. describe using a diagram charging by rubbing and charging by induction; and
2. describe experiments to show electrostatic charging by induction
What you need:
Paper and pen
What to do:
Observe and describe the following diagrams below by answering the guide
questions. The guide questions on nos. 1 to 3 and nos. 4 to 6 are based on Figure 9
and 10 respectively. Write your answers on a separate sheet of paper.
Fig.9
Source:Electricity Physics, 2020/12/11 20:14:47, pdf, page 13
Fig.10
Source:Electricity Physics, 2020/12/11 20:14:47, pdf, page 12
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
9
Guide Questions:
1. What are the charges of the two spheres before a positively charged glass rod is
brought near to one of the spheres? Why do they have that type of charge(s) when
they are in contact to each other? (Refer to Figure 9a)
2. Why is the sphere on the left becomes negatively charged when a positively
charged glass rod is brought near to it? (Refer to Figure 9b)
3. What happens to the spheres when they are separated first and the rod was
removed then? What type of charging do the spheres experience? (Refer to Figure
9c and 9d)
4. What happens to the top of stem and metal foil leaves of electroscope after the
positively charged glass rod is brought near to the tip of it? (Refer to Figure 10a)
5. What happens to the positively charged glass rod and to the electroscope when
the rod came in contact with the ball of electroscope? (Refer to Figure 10b)
6. Where do the excess charges go when the glass rod is removed? (Refer to Figure
10c)
3
Practical
application is
scientifically
explained
consistent to
the concepts,
and has no
misconceptions.
Rubric for Guide Questions 1 to 6
2
1
Practical application Practical application
is scientifically
is explained
explained consistent consistent to the
to the concepts, but concepts but with
with minimal
misconceptions.
misconceptions.
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
10
0
No discussion.
Activity 3. Electric Field Lines
Objective
The learners should be able to describe an electric field as a region in which an
electric charge experiences a force
What you need:
Paper and pen
What to do:
1. Write the type of charge(s) of the object(s) shown by the images in Column A at
Column B.
2. Describe the images in terms of the direction of arrows, density, strength, and
attraction of the electrical fields and write your description at Column C. Number
1 is answered for you as your guide.
Column A
1.
Fig.11
Source:Electricity
Physics,
20:14:47, pdf, page 19
2020/12/11
2.
Fig.12
Source:Electricity
Physics,
20:14:47, pdf, page 19
2020/12/11
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
11
Column B
Column C
Positive
charge
The direction of the
arrows are outward.
3.
Fig.13
Source:Electricity
Physics,
20:14:47, pdf, page 19
2020/12/11
4.
Fig.14
Source:Electricity
Physics,
20:14:47, pdf, page 19
2020/12/11
5.
Fig.15
Photo:Electricity
Physics,
20:14:47, pdf, page 22
2020/12/11
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
12
6.
Fig.16
Source:Electricity
Physics,
20:14:47, pdf, page 22
2020/12/11
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
13
Activity 4. Solve It, Coulomb!
Objective
The learners should be able to:
1. calculate the net electric force on a point charge exerted by a system of point
charges; and
2. calculate the electric field due to a system of point charges using Coulomb’s law
and the superposition principle
What you need:
Paper, pen, scientific calculator (optional)
What to do:
Answer the following problems. Write your solutions on a separate sheet of paper.
1. A point charge of +1.10 × 10−6 C is 11.0 cm distant from a second point charge of
−1.50 × 10−6 C. Calculate the magnitude of the force on each charge.
2. What must be the distance between point charge q1 = 16.0 μC and point charge q2
= −37.0 μC for the electrostatic force between them to have a magnitude of 5.70 N?
3. The average distance r between the electron and the proton in the hydrogen atom
is 5.3 × 10-11 m. What is the magnitude of the average electrostatic force that acts
between these two particles?
4. Three charges, each equal to +3.2 μC, are placed at three corners of a square
0.500 m on a side, as shown in the Figure 17. Find the magnitude and direction
of the net force on charge number 3.
Fig.17
Source:https://www.csun.edu/~rd436460/100B/
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
14
Reflection
Coulomb's Law has many great applications to modern life, from Xerox machines to
laser printers, to powder coating.
If Xerox machines and laser printers were not invented, what do you think is its
impact to our education today? Write your 5-sentence answer in a separate sheet of
paper.
3
Practical application
is scientifically
explained consistent
to the concepts, and
has no
misconceptions.
Rubrics
2
1
Practical application Practical application
is scientifically
is explained
explained consistent consistent to the
to the concepts, but concepts but with
with minimal
misconceptions.
misconceptions.
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
15
0
No discussion.
References for learners:
Christensen, Erik, OpenStax. Electricity Physics, M. Ahmad, 2020
Young, Hugh D., Roger A. Freedman. Sears and Zemansky's University Physics with
Modern Physics. 13th ed. Boston, MA: Pearson Learning Solutions, 2012.
California State University Northridge. “Chapter 19 Electric Charges, Forces, and Fields.”
Accessed on January 10, 2021.
https://www.csun.edu/~rd436460/100B/lectures/chapter19-1-3.pdf
HCC Learning Web. “Chapter 23 Electric Fields.” Accessed on January 12, 2021.
https://learning.hccs.edu/faculty/kam.chu/powerpoint-presentation-foruniversity-physics-ii/chapter-23/view
Online Physics Tutorials. “Types of Charging”. Accessed on January 10, 2021.
https://www.physicstutorials.org/home/electrostatics/types-of-charging
Physics LibreTextsTM. “5.4: Coulomb's Law”. Accessed on February 2, 2021.
https://phys.libretexts.org/Bookshelves/University_Physics/Book%3A_University
_Physics_(OpenStax)/Map%3A_University_Physics_II__Thermodynamics_Electricity_and_Magnetism_(OpenStax)/05%3A_Electric_Charg
es_and_Fields/5.04%3A_Coulomb%27s_Law?fbclid=IwAR1oAJNZz5O_WLraq8IcVv
ANwnOVm0nnoRk1_oTSv_PLb5yAy_jEuKIEvqo
The Physics Classroom. “Coulomb's Law”. Accessed on January 10, 2021.
https://www.physicsclassroom.com/class/estatics/Lesson-3/Coulomb-s-Law
Tennessee Tech University. “Chapter 1. Electric Charge; Coulomb’s Law”. Accessed on
January 12, 2021
https://www2.tntech.edu/leap/murdock/books/v4chap1.pdf
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
16
Answers Key
Answers Key
Author: AR A. Ranesis
School/Station: Alba Integrated School
Division: Surigao del Sur Division
email address: ar.ranesis@deped.gov.ph
17