General
Physics 2
12
General Physics 2 – Grade 12
Quarter 4 – Module 1: Electromagnetic Induction
First Edition, 2020
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General
Physics 2
12
Quarter 4
Self-Learning Module 1
Electromagnetic Induction
Introductory Message
For the Facilitator:
Welcome to the General Physics 2 Grade 12 Self-Learning Module on
Electromagnetic Induction!
This Self-Learning Module was collaboratively designed, developed, and
reviewed by educators from the Schools Division Office of Pasig City headed by its
Officer-in-Charge Schools Division Superintendent, Ma. Evalou Concepcion A.
Agustin, in partnership with the City Government of Pasig through its mayor,
Honorable Victor Ma. Regis N. Sotto. The writers utilized the standards set by the K
to 12 Curriculum using the Most Essential Learning Competencies (MELC) in
developing this instructional resource.
This learning material hopes to engage the learners in guided and independent
learning activities at their own pace and time. Further, this also aims to help learners
acquire the needed 21st-century skills especially the 5 Cs, namely: Communication,
Collaboration, Creativity, Critical Thinking, and Character while taking into
consideration their needs and circumstances.
In addition to the material in the main text, you will also see this box in the
body of the module:
Notes to the Teacher
This contains helpful tips or strategies that
will help you in guiding the learners.
As a facilitator, you are expected to orient the learners on how to use this
module. You also need to keep track of the learners' progress while allowing them to
manage their learning. Moreover, you are expected to encourage and assist the
learners as they do the tasks included in the module.
For the Learner:
Welcome to the General Physics 2 Self-Learning Module on Electromagnetic
Induction!
This module was designed to provide you with fun and meaningful
opportunities for guided and independent learning at your own pace and time. You
will be enabled to process the contents of the learning material while being an active
learner.
This module has the following parts and corresponding icons:
Expectations - This points to the set of knowledge and skills
that you will learn after completing the module.
Pretest - This measures your prior knowledge about the lesson
at hand.
Recap - This part of the module provides a review of concepts
and skills that you already know about a previous lesson.
Lesson - This section discusses the topic in the module.
Activities - This is a set of activities that you need to perform.
Wrap-Up - This section summarizes the concepts and
application of the lesson.
Valuing - This part integrates a desirable moral value in the
lesson.
Posttest - This measures how much you have learned from the
entire module.
EXPECTATIONS
The module is about Faraday’s Law for Electromagnetic Induction.
After going through this module, you are expected to:
1. identify the factors that affect the magnitude of the induced emf
(electromotive force) and direction of the induced current (Faraday’s Law);
2. compare
and
contrast
electrostatic
electric
field
and
nonelectrostatic/induced electric field; and
3. recognize some applications of electromagnetic induction.
PRETEST
Choose the letter of the BEST correct answer. Write the chosen letter in your
notebook.
1. A voltage will be induced in a wire loop when the magnetic field within
that loop
A. changes
B. aligns with the electric field
C. is at the right angle to the electric field
D. converts to magnetic energy
2. If you change the magnetic field in a closed loop of wire, you induce
in the loop a
A. current
B. voltage
C. electric field
D. all of the above
A.
3. Which of the following equations correctly describes Faraday’s law of
induction?
A. 𝑒𝑚𝑓 = − 𝑁
B. 𝑒𝑚𝑓 = 𝑁
∆𝐴𝐵 𝑡𝑎𝑛 𝜃
∆𝑡
∆𝐴𝐵 𝑐𝑜𝑠 𝜃
C. 𝑒𝑚𝑓 = − 𝑁
D. 𝑒𝑚𝑓 = − 𝑀
∆𝑡
∆𝐴𝐵 𝑐𝑜𝑠 𝜃
∆𝑡
∆𝐴𝐵 𝑐𝑜𝑠 𝜃
∆𝑡
4. The essential concept in an electric motor and a generator is
B. Coulomb’s law
C. Ohm’s law
D. Faraday’s law
E. Newton’s second law
5. Which of the following would not increase the emf produced by a
generator?
A. rotating the generator coil faster
B. increasing the strength of the generator magnets
C. increasing the number of turns of wire in the coil
D. reducing the cross-sectional area of the coil
RECAP
Given the different illustration of a magnet, complete the table by giving some
characteristics and properties of the magnetic field:
(Photo Credits: PresentationExpress Conceptual
Physics, Pearson)
(Photo Credits: Google Image)
(Photo Credits: PresentationExpress Conceptual Physics,
Pearson)
(Photo Credits: Google Image)
LESSON
Copyright © https://google/images
A
B
Are you familiar with picture A? How about picture B?
How do these objects work?
What can you say about the picture on the left?
Can you light a bulb or detect current without
any power source or battery? How?
Copyright © : PresentationExpress Conceptual Physics
ELECTROMAGNETIC INDUCTION:
In 1831, two physicists, Michael
Faraday in England and Joseph Henry in
the
United
States,
independently
discovered
that
magnetism
could
produce an electric current in a wire.
Their discovery was to change the world
by making electricity so commonplace
that it would power industries by day and
light up cities by night.
They discovered the principle of
electromagnetic induction at almost
the same time but in countries separated
by the ocean!
Copyright ©
https://images.app.goo.gl/V9h4FvZvfmXu1u7C8https://image
s.app.goo.gl/V9h4FvZvfmXu1u7C8
To see how an emf can be induced by a changing magnetic field, copy this link
on your browser and explore the simulation with the bar magnet and the coil of wire,
using
the
ammeter
or
the
bulb
as
an
indicator
or
sensor
https://phet.colorado.edu/sims/cheerpj/faraday/latest/faraday.html?simulation=
generator
In the simulation, try to move the bar magnet in and out of the coil and observe
the bulb and the direction of the ammeter needle. Change the speed of the motion of
the bar magnet and take note of your observations.
Consider a loop of wire connected
to a galvanometer. When a magnet is
moved
toward
the
loop,
the
galvanometer needle deflects in one
direction, as shown in figure a. When
the magnet is moved away from the
loop, the needle deflects in the opposite
direction, as shown c. When the magnet
is held stationary relative to the loop in
figure b, no deflection is observed.
Finally, if the magnet is held
stationary and the loop is moved either
toward or away from it, the needle
deflects. From these observations, we
conclude that the loop “knows” that the
magnet is moving relative to it because
it experiences a change in a magnetic
field. Thus, it seems that a relationship
exists between current and changing
magnetic fields.
Copyright © : Physics, Serway 5th Edition, Faraday’s Law of Induction
A current is set up even though no batteries are present in the circuit! We call
such a current an induced current and say that it is produced by an induced emf.
FARADAY’S EXPERIMENT:
 A
primary
coil
is
connected to a switch and
a battery.
 The wire is wrapped
around an iron ring.
 A secondary coil is also
wrapped around the iron
ring.
 There is no battery
present in the secondary
coil.
 The secondary coil is not
connected to the primary
coil.
 At an instant the switch is
closed,
the
ammeter
changes from zero in one
direction
and
then
returns to zero.
 When the switch is
opened, the ammeter
changes in the opposite
direction
and
then
returns to zero.
 The ammeter reads zero
when there is a steady
current or when there is
no current in the primary
circuit.
An electric current can be induced in a loop of wire by changing the magnetic
field. This would be the current in the secondary circuit. The induced current exists
only while the magnetic field through the loop is changing. Therefore, an induced
emf (electromotive force) is produced in the loop by the changing magnetic field.
Faraday concluded that an electric current can be induced in a circuit (the
secondary circuit in our setup) by a changing magnetic field. In effect, the
secondary circuit behaves as though a source of emf were connected to it for a short
time. It is customary to say that an induced emf is produced in the secondary
circuit by the changing magnetic field.
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION:
The emf (electromotive force) induced in a circuit is directly proportional to the
time rate of change of the magnetic flux through the circuit. Mathematically,
𝒆𝒎𝒇 = −
∆ 𝝓𝒎
∆𝒕
If the circuit consists of N loops, Faraday’s law states that the induced voltage
in a coil is proportional to the product of the number of loops, the cross-sectional area
of each loop, and the rate at which the magnetic field changes within those loops.
𝒆𝒎𝒇 = − 𝑵
The magnetic flux is given by
∆𝝓𝒎
∆𝒕
𝝓𝒎 = 𝑨𝑩 𝒄𝒐𝒔 𝜽.
Ways of Inducing an emf:
1. The magnitude of the magnetic field can change in time.
2. The area enclosed by the loop can change with time.
3. The angle between the magnetic field and the normal to the loop can change
with time
APPLICATION OF ELECTROMAGNETIC INDUCTION:
Electromagnetic Induction is the production of an electromotive force (i.e.,
voltage) across an electrical conductor due to its dynamic interaction with a magnetic
field. Induction is used in power generation and power transmission, and it’s worth
taking a look at how that’s done. There are other effects with some interesting
applications to consider, too, such as eddy currents.
An Electric Generator – An electric motor is a device for transforming
electrical energy into mechanical energy; an electric generator does the reverse, using
mechanical energy to generate electricity. At the heart of both motors and generators
is a wire coil in a magnetic field. The same device can be used as a motor or a
generator.
Eddy Currents – An eddy current is a swirling current set up in a conductor
in response to a changing magnetic field.
Transformers – Electricity is often generated a long way from where it is used
and is transmitted long distances through power lines.
ACTIVITIES
Activity 1 – Induced EMF & Induced Current
Using the galvanometer and the description of the movement of the magnet, write
and explain your observations based on the galvanometer reading on the space
provided:
Illustration
Description
The magnet is
moved through a
coil of wire.
(Photo Credits: Google Image)
The magnet is
moved faster
through the coil
of wire.
(Photo Credits: Google Image)
Loops of wire
were added
(Photo Credits: Google Image)
The magnet is
pulled out rather
than pushed in
(Photo Credits: Google Image)
Observation/s
Activity 2 – Practice Problems
Apply Faraday’s Law of Electromagnetic Induction in solving word problem/s.
1. A coil with 25 turns of wire is wrapped around a hollow tube with an area of
1.8 m2. Each turn has the same area as the tube. A uniform magnetic field is
applied at a right angle to the plane of the coil. If the field increases uniformly
from 0.00 T to 0.55 T in 0.85 s, find the magnitude of the induced emf in the
coil. If the resistance in the coil is 2.5 Ω, find the magnitude of the induced
current in the coil.
2. A coil consists of 200 turns of wire having a total resistance of 2.0. Each turn
is a square of side 18 cm, and a uniform magnetic field directed perpendicular
to the plane of the coil is turned on. If the field changes linearly from 0 to 0.50
T in 0.80 s, what is the magnitude of the induced emf in the coil while the field
is changing? What is the magnitude of the induced current in the coil while
the field is changing?
WRAP-UP
Complete the table about
what you have learned about this
module:
VALUING/APPLICATION
POWER TRANSMISSION:
Power transmission uses transformers to
increase voltage for long-distance
transmission and decrease it before it reaches
your home.
Copyright © : PresentationExpress Conceptual Physics
Why is almost all electrical energy sold
today in the form of alternating current?
POSTTEST
Choose the letter of the best answer. Write the chosen letter in your notebook.
1. What is electromagnetic induction?
A. The production of an electric current created by a varying magnetic
field
B. The production of the magnetic field, accomplished by running a
current through a coil of wire
C. Creating electromagnetic fields by any purposeful means
D. Building a magnet
2. If a wire is moved perpendicular to the magnetic field, what is induced
across the ends of the wire?
A. area
B. coil
C. magnetic field
D. potential difference
3. All matters are said to be neutral wherein the numbers of electron and protons are
equal so once charges it do not stay for a long time because of the following factors
except;
A. faster
B. slower
C. in opposite direction
D. parallel to the magnetic field
4. the amount of induced potential difference can be increased if the wire is
moved in the magnetic field ___________
A. generating electricity
B. energy efficient cookers and burners
C. energy-efficient motors
D. using a magnet to separate scrap metal parts
5. Which of the following is NOT a way that a magnetic field can be varied to
induce a current in a wire?
A. Move the coil in and out of the magnetic field
B. Rotate the coil inside the magnetic field
C. Move the coil once it is already fully inside the magnetic field
D. Change the strength of the magnetic field
KEY TO CORRECTION
2. emf = 4.1 V
I = 2.0 A
Posttest:
1. A
2. D
3. A
4. D
5. B
1. emf = - 29 V
I = - 12 A
Activity 2:
Pretest:
1. A
2. D
Recap: (answers may vary)
Activity 1: (answers may vary)
3. C
4. C
5. D
R E F E R E N CE S
Physics by Holts, Rineheart and Winston, Electromagnetic Induction, Chapter 20
Serway, Physics 5th Edition PDF
Presentation Express, Conceptual Physics, Electromagnetic Induction, Chapter 37.
https://www.assignmentpoint.com/science/physics/electromagneticinduction.html
https://phet.colorado.edu/sims/cheerpj/faraday/latest/faraday.html?simulation=
generator