Electromagnetic Induction Test

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Electromagnetic Induction Test - 41

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Weekly Quiz Competition

Question 1
1 / -0

A conducting rod AB moves parallel to X-axis in a uniform magnetic field, pointing in the positive X-direction. The end A of the rod gets

A
positively charged

B
negatively charged

C
neutral

D
first positively charged and then negatively charged

Solution

According to right hand palm rule, the Lorentz force on free electrons in the conductor will be directed towards and B. Hence, the end A gets positively charged.
Question 2
1 / -0

A coil in a simple generator has 200 turns.Now the number of turns in the coil increases to 500. What will be its effect:

A
current produced will increase

B
voltage produced will increase

C
both

D
none

Solution

By law of conservation of energy, mechanical power converted =electrical power produced assuming no losses
i.e. $$VI = $$ constant.
When turns are increased, voltage induced increases, since voltage is proportional to to number of turns.
Hence, current reduces.
Question 3
1 / -0

Consider a current carrying coil placed in a magnetic field. What are the requirements for induced current to flow as per electromagnetic induction.

A
Coil of wire carrying current

B
Change in magnetic field associated with the coil

C
Both A and B

D
None

Solution

When magnetic flux through a coil changes, emf is induced in it. Current carrying coil is not required for above.
Question 4
1 / -0

Which of the following will not increase voltage in a simple generator?

A
Increasing the number of turns in armature coil.

B
Winding the coil on a soft armature.

C
Increasing the size of the gap in which the armature turns.

D
Increasing the speed of rotation.

Solution

Voltage/current produced in a generator can be increased by:
a) using a powerful electromagnet to make the magnetic field stronger in place of a permanent magnet.
b) by winding the coil round a soft iron core to increase the strength of magnetic field.
c) by using a coil with more turns.
d) by rotating the coil faster.
e) by using a coil with a larger area.
Question 5
1 / -0

A jet plane is travelling towards west at a speed of 1600 km/h. What is the voltage difference developed between the ends of the wing having a span of 25 m, if the Earths magnetic field at the location has a magnitude of 5 $$\times 10^{-4}$$ T and the dip angle is $$30^o$$.

A
4.1 V

B
2.2 V

C
3.2 V

D
3.8 V

Solution

Vertical component of B,
$$B \sin \delta = 5 \times 10^{-4} \times \sin (30)=2.5 \times 10^{-4} T$$
EMF, $$E=Blv$$
$$E=2.5 \times 10^{-4} \times 25 \times 1800 \times \dfrac{5}{18}=3.125 V$$
Question 6
1 / -0

The back emf in a DC motor is maximum when

A
the motor has picked up maximum speed.

B
the motor has just started moving.

C
the speed of motor is still on increase.

D
the motor has just been switched off.

Solution

The value of back emf is proportional to the motor speed. So, back emf is maximum when the motor has picked up the maximum speed.
Question 7
1 / -0

What is the self inductance of a coil in which an induced emf of $$2V$$ is set up, when the current is changing at the rate of $$4As^{-1}$$

A
$$0.5\ mH$$

B
$$0.05\ H$$

C
$$2\ H$$

D
$$0.5\ H$$

Solution

Induced emf in a inductor $$L$$ is: $$\varepsilon = L \dfrac{di}{dt}= L \times 4$$
$$\Rightarrow 2 = L \times 4 $$
$$\Rightarrow L = 0.5\: H$$
Question 8
1 / -0

You have a coil and a bar magnet. You can produce an electric current by:

A
moving the magnet but not the coil

B
moving the coil but not the magnet

C
moving either the magnet or the coil

D
using another DC source

Solution

Electric current can be produced by either moving a coil or a magnet and hence e.m.f is induced.
Question 9
1 / -0

The current produced in a closed coil, where magnetic lines of force rapidly change within it is called:

A
direct current

B
alternating current

C
induced current

D
none of these

Solution

The property due to which a changing magnetic field within a closed conducting coil induces electric current in the coil is called electromagnetic induction. The current produced in a closed coil, where magnetic lines of force rapidly change within it is called Induced current.
Question 10
1 / -0

A straight conductor 0.1 m long moves in a uniform magnetic field 0.1 T. The velocity of the conductor is 15 m/s and is directed perpendicular to the field. The emf induced between the two ends of the conductor is:

A
0.10 V

B
0.15 V

C
1.50 V

D
15.00 V

Solution

Given, length of conductor l= 0.1 m
Magnetic field = $$0.1T$$
Velocity = $$15m/s$$

Emf Induced = $$Blv$$ = $$ 0.1X0.1X15 = 0.15V $$

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Re-Attempt Weekly Quiz Competition

Electromagnetic Induction Test - 41

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Electromagnetic Induction Test - 41

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SHARING IS CARING

Question 1

positively charged

negatively charged

neutral

first positively charged and then negatively charged

Solution

Question 2

current produced will increase

voltage produced will increase

both

none

Solution

Question 3

Coil of wire carrying current

Change in magnetic field associated with the coil

Both A and B

None

Solution

Question 4

Increasing the number of turns in armature coil.

Winding the coil on a soft armature.

Increasing the size of the gap in which the armature turns.

Increasing the speed of rotation.

Solution

Question 5

4.1 V

2.2 V

3.2 V

3.8 V

Solution

Question 6

the motor has picked up maximum speed.

the motor has just started moving.

the speed of motor is still on increase.

the motor has just been switched off.

Solution

Question 7

$$0.5\ mH$$

$$0.05\ H$$

$$2\ H$$

$$0.5\ H$$

Solution

Question 8

moving the magnet but not the coil

moving the coil but not the magnet

moving either the magnet or the coil

using another DC source

Solution

Question 9

direct current

alternating current

induced current

none of these

Solution

Question 10

0.10 V

0.15 V

1.50 V

15.00 V

Solution

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