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Republic of the Philippines
Department of Education
ACTIVITY SHEETS IN GENERAL PHYSICS 2
QUARTER 3, WEEK 1
EXPERIENCING ELECTRICITY
MELC:
Describe using a diagram charging by rubbing and charging by induction (STEM_GP12EM-IIIa-1) Explain the role of electron transfer in electrostatic charging by rubbing (STEM_GP12EM-IIIa-2) Describe experiments to show electrostatic charging by induction (STEM_GP12EM-IIIa-3) Calculate the net electric force on a point charge exerted by a system of point charges (STEM_GP12EM-IIIa-6) Describe an electric field as a region in which an electric charge experiences a force (STEM_GP12EM-IIIa-7) Calculate the electric field due to a system of point charges using Coulomb’s law and the superposition principle (STEM_GP12EM-IIIa-10) Calculate electric flux (STEM_GP12EM-IIIb-12)
Prepared by:
MICHELLE A. AGULAY
Master Teacher I
BACKGOUND INFORMATION
EXPERIENCING ELECTRICITY
Electricity is everywhere around us. The incandescent bulbs that light our homes, the batteries that power up our appliances, the transmission lines that supply energy to our homes are but few of the many things that utilize electricity. There are also some far more simple phenomena that let us experience electricity, and many of these are indeed amazing. However, if we understand the principles behind electricity, we will find out that what lies behind these wonders are just simple laws of nature.
Have you ever experienced ironing a piece of linen cloth or pair of pants? What do you feel when you put your skin near the just ironed cloth? Is there a crackling sound produced? What do you feel when you immediately grab a doorknob after walking through a carpeted floor? How do you explain the slight shock that you feel considering that there is no physical connection to a source of electricity in these instances? Do you remember what happens when you rub an object against your hair and put such object near a piece of paper? You used to play with this at school and were once amazed. But now do you know that by explaining this phenomenon, we will come to an understanding of the nature of electricity?
The activities that follow give fundamental concepts and ideas on electricity and its effects and applications in our everyday living. Specifically, it tackles on the development of electricity, static electricity, charges and Coulomb’s Law and conductors and insulators.
KEY CONCEPTS, EQUATIONS, AND SAMPLE PROBLEM SOLVING
Concept Discussion Development of Electricity
Concept Discussion the stronger the field. And the field varies inversely with the square of the distance between the charges. This means that the greater the distance, the weaker the force becomes. Coulomb’s law states that the force one charge exerts on another is directly proportional to the magnitudes of the charges and inversely proportional to the square of the distance between them This relationship can be written as a formula:
In vacuum the value of k is 9 x 10^9 N.m^2 /C 2.^ Let us interpret the formula using the following diagrams:
According to this law, when two positively-charged objects (2C and 4C, respectively) are brought near each other within a distance of 20 cm, the force of attraction between the two charges is
Electric flux and Gauss’s Law
(^) Electric flux is the rate of flow of the electric field through a given area. Electric field : A region of space around a charged particle, or between two voltages; it exerts a force on charged objects in its vicinity.
Concept Discussion Electric flux and Gauss’s Law
Gauss’s Law states that the electric flux passing through a closed surface is equal to the ratio of total charge enclosed by that surface to the permittivity of free space. Φ CLOSED SURFACE = q / ε Where (^) q total charge and (^) / ε0 permittivity This means that the electric flux passing through a closed surface is independent of shape or area of the surface.
SAMPLE PROBLEMS
Example 1: Find the magnitude of the force between two charges of 1 C each
that are 2 m apart.
Given: q 1 and q 2 = 1 C; d = 2m
Solution: = 9 x 10^9 N.m^2 /C^2 (1C)(1C) = 2.25 x 10^9 N
(2m)^2
Example 2: A charge of 5 x10-9^ C is attracted by a charge of – 3x10-7^ C with a
force of 0.135 N. How far apart are they? (Hint: manipulate the equation to get an expression for d)
Given: q 1 = 5 x10-9^ C q 2 = – 3x10-7^ C F = 0.135 N
Solution: 𝑑 =
√𝑘𝑞 1 𝑞 2 √F
𝑑 = √9 x 10^9 N.𝑚^2 /𝑐^2 (5 x10−9C)(–3x10−7^ C) √0.135N d = 𝟑. 𝟖𝟕𝟐𝟗𝒙𝟏𝟎−𝟏𝟎^ m
Figure Name Conductor/Insulator
Title of the Activity: DIAGRAM ANALYSIS: Let’s Trace It!
Most Essential Learning Competency :
Describe using a diagram charging by rubbing and charging by induction (STEM_GP12EM-IIIa-1)
Directions: Draw the electric field that surrounds the charges given below.
1. A positive charge 2. A negative charge
3.Two positive charges and one negative charge
4. A negative charge and a positive metallic bar
5. A positive charge and a negative metallic ring 6. What information can be concluded in the figure?
Title of the Activity: PROBLEM ANALYSIS: Let’s Work Out!
Most Essential Learning Competency :
Calculate the net electric force on a point charge exerted by a system of point charges (STEM_GP12EM-IIIa-6) Calculate the electric field due to a system of point charges using Coulomb’s law and the superposition principle (STEM_GP12EM-IIIa-10) Calculate electric flux (STEM_GP12EM-IIIb-12)
Directions: Solve the following problems completely and accurately.
Note: Electric Field is defined as the force felt by a positive test charge.
E or Fe = F/q or F=qE [Unit of E or Fe, (Electric Field) is N/C) Where : F – force (newton , N) q – electric charge (Coulomb, C)
- Two point charges, QA = +8 μC and QB = - 5 μC, are separated by a distance r = 10 cm. What is the magnitude of the electric force. The constant k = 8.988 x 109 Nm^2 C^2
- A charge of 5.67 x 10-18 C is placed 3.5 x 10 -6 m away from another charge of – 3.79 x 10-19 C. What is the force of attraction between them?
- How far apart must two electrons be if the force between them is 1.0 x 10 - 12 N?
ANSWER KEY:
A.
- Elec-field
- Elec-charge
- Elec-field
- Elec-charge
- Elec-field B.
Figure Name Conductor/Insulator
6. Spoon Conductor
7. Door knob Conductor
8. Surgical glove Insulator
9. Aluminum Conductor
10. Tire Insulator
Answers may vary
1. F = 4 X 10 -9^ N
2. F = 125 N
- q = 90 X 10-^6
- Fe = 1.58 x 10-15 N
- d = 1.52 x 10-8 m
Answers may vary
Title of the Activity: Let’s Be ELECtrified!
Title of the Activity: DIAGRAM ANALYSIS: Let’s Trace It!
Title of the Activity: PROBLEM ANALYSIS: Let’s Work Out!
Title of the Activity: THINK ABOUT THIS: The Concept Behind!
References
Books:
Alternative Delivery Mode Learning Resource Standards prescribed by the Department of education Central Office. 2020
Department of Education Central Office. Most Essential Learning Competencies (MELCs). 2020.
Hewitt, P.G. Conceptual physics. USA: Addison-Wesley Publishing Co., Inc. 1997.
Navasa, D. and Valdez, B.J. Physics. Quezon City: Sibs Publishing House, Inc.
Salmorin, L.M. and Florido, A. Physics IV. Quezon City: Abiva Publishing House, Inc. 2004.
See Tho Weng Fong Science for Secondary Schools. Singapore: Longman Singapore Publishers. 1995.
Santos, G.N C. and Ocampo J.P. RBS Science and Technology Series E-Physics IV. Sampaloc, Manila. Rex Book Store Inc. 2003.
Taffel, A. Physics: Its methods and meanings. USA: Prentice Hall Publishers.1992.
Tan, M TIMSS-LIKE Test Items in Science and Mathematics. DOST-SEI, UPNISMED, Pundasyon Para sa mga Guro ng Agham at Matematika, Ink.
Tillery, B.W. Physical science. Singapore: WCB McGraw-Hill. 1999.
