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Published by haz imah, 2019-08-28 00:43:34

EXAMPLE-induction

EXAMPLE-induction

EXAMPLE OF
PROBLEM SOLVING

Induced Emf

× × × ×A × × × × × ×

Q1 × × × × × × × × × ×

×× ××××××××
×× ××××××××
× × × ×B × × × × × ×

A circular coil has 200 turns and diameter 36
cm. The resistance of the coil is 2.0 Ω. A
uniform magnetic field is applied
perpendicularly to the plane of the coil.
Then, the field is changes uniformly from 0.5
T to 0 T in 0.8s.

Q1

a. Find the induced e.m.f. & current
in the coil while the field is changed.

b. Determine the direction of the
current induced.

Suggest Answer

(a)1. List the information given;
N= 200
d = 36 cm = 36 X 10-2 m
R=2Ω
B = 05 T to 0 T
∆t = 0.8 s

2. Choose a suitable formula :

( * N and A constant, θ = 0° )

3. Apply

Before that, find the area of the coil, A

Thus, the induced emf is

#

To determine the value of induced current,
Using:

#

(b) 1. List the information given;

X : B is into the page

2. Choose a suitable formula :
Lens Law : Induced current will try to

prevent the decrease in flux

I induced

3. Apply the formula.

Right Hand Rule.

Thus, induced current is in

clockwise direction. #

Q2

A loop of area 0.10 m2 is rotating at 60 rev/s
with its axis of rotation perpendicular to a
0.20 T magnetic field.

Q2

a. If there are 1000 turns on the loop, what
is the maximum voltage induced in the
loop?

b. When the maximum induced voltage
occurs, what is the orientation of the loop
with respect to the magnetic field?

Suggest Answer

(a) 1. List the information given;

A= 0.1 m2
B = 0.2 T
ω = 60 rev/s =

= 120 π rad/s
N = 1000

2. Choose a suitable formula :
=

Note for maximum value, sin ωt = 1.0

3. Apply the formula.

Thus, maximum voltage induced is

#

(b) 1. List the information given;

Axis of rotation perpendicular to magnetic field, B

2. Choose a suitable formula :

=

3. Apply the formula :

Note for maximum value, sin ωt = 1.0

= sin

Thus, the orientation of the loop

must be parallel to the field #

Q3 x xx xx x vxx xx x x x
xx x xx xx x xx x x x
xx x xx xx xx x x x
xx x xx xx xx x x
R =x 6 Ωx x xx xx x L =x 1.2xm x x
xx x xx xx xx x x
xx x xx xx xx x x x
xx xx xx x
xx x
xx

xx

Figure 3

Based on figure 3, assume that a
uniform 2.50 T magnetic field is
directed into the page.

Q3

a. At what speed should the bar
(blue) be moved to produced a current
of 0.5A in the resistor?

b. What is the direction of the
induced current ?

Suggest Answer

(a) 1. List the information given;

R=6Ω
L = 1.2m
B = 2.50 T
I = 0.5A
v=?

2. Choose a suitable formula :

= sin

3. Apply the formula :
Thus, the speed of the bar is

#

(b) 1. List the information given; B

B : into the page
v = right

2. Choose a suitable formula:
I/F

Fleming’s Left Hand Rule

v

3. Apply the formula :

xx xx xx xx xx xx xx
xx xx xx xx xx xx xx
xx xx xx xx xx
xx xx x x vx x
xx x x R =x6 Ωx xx xL =x1.2m
xx xx xx xx
xx xx xx xx xx xx xx
xx xx xx xx xx
xx xx xx xx xx

Thus the direction of the induced

current is anticlockwise #

Q4

A single turn of wire of cross-
sectional area 5.0 cm2 is at 90o to
a magnetic field of 0.02 T, which
is reduced to 0 in 10 s at a steady
rate. What is the e.m.f. induced?

Suggest Answer

1. List the information given;

A = 5.0 cm2
θ = 0°
B = 0.02 T
t = 10 s
N=1

2. Choose a suitable formula :

= − ( )


3. Apply the formula :

Thus, the induced emf is

= −(1) 0.02 5.0 × 10−4 cos 0°
= −1.0 × 10−5 # 10

× × A× × × × × ×

Q5

×× ××××××

× × B× × × × × ×

The flexible loop has a radius of 12 cm
and is in a magnetic field of strength
0.15 T. The loop is grasped at point A
and B and stretched until its area is
nearly zero.

Q5

If it takes 0.20 s to close the loop, find
the magnitude of the average induced
emf in it during this time.

× × A× × × × × × ×× ×× ×× ××

×× ×××××× ×× ×× ×× ××

× × B× × × × × × ×× ×× ×× ××

Suggest Answer

1. List the information given;

r = 0.12 m
∆t = 0.2 s
B = 0.15 T to 0 T

2. Choose a suitable formula :

3. Apply the formula :
Thus, induced emf is


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