Electromagnetic Induction Test

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Electromagnetic Induction Test - 19

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Question 1
1 / -0

The average self-induced emf in a $$25 m H$$ solenoid when the current in it falls from $$0.2 A$$ to $$0 A$$ in $$0.01$$ second, is

A
$$0.05 V$$

B
$$0.5 V$$

C
$$500 V$$

D
$$50 V$$

Solution

$$emf=L\dfrac { di }{ dt } $$
$$=25\times { 10 }^{ -3 }\times \dfrac { 0.2 }{ 0.01 } $$
$$= 0.5V$$
Question 2
1 / -0

What is the SI unit of self-inductance ?

A
Henry

B
Tesla

C
Weber

D
Gauss

Solution

Henry (symbol H) is the SI derived unit of self-inductance.
Question 3
1 / -0

A coil of self-inductance L is connected in series with a bulb B and an AC source. Brightness of the bulb decreases when :

A
frequency of the AC source is decreased

B
number of turns in the coil is reduced

C
a capacitance of reactance $$X_C = X_L$$is included in the same circuit

D
an iron rod is inserted in the coil

Solution

Self-inductance of a coil is,

$$L=\dfrac{\mu_0\mu_rN^2A}{l}$$

Current flow through the circuit,

$$I= \dfrac{E}{(w^2L^2+R^2)^{1/2}}$$

Current in the circuit decrease with increasing self-inductance,

$$L\alpha\mu_r$$.

When an iron rod is inserted in the coil, self-inductance increases, and the current decreases. The brightness of the bulb decreases.
Question 4
1 / -0

When the flux linked with a coil changes :

A
current is always induced

B
an emf and a current are always induced

C
an emf is induced but a current is never induced

D
an emf is always induced and a current is induced when the coil is a closed one

Solution

$$EMF\quad =-\dfrac { d\phi }{ dt } $$, where $$\phi $$ is flux
So, whenever flux changes, EMF is induced. But ,current will be induced only when the coil is a closed one.
Question 5
1 / -0

If ‘N’is the number of turns in a coil, the value of self inductance varies as

A
$$N^{0} $$

B
$$N$$

C
$$N^{2} $$

D
$$N^{-2} $$

Solution

Formula for self-inductance of a coil: $$L = \frac{\mu_0 N^2 A}{l}$$
Hence , it varies as $$N^2$$
Question 6
1 / -0

The phenomenon of electromagnetic induction was discovered by

A
Lenz

B
Maxwell

C
Fleming

D
Faraday

Solution

The phenomenon of electromagnetic induction was discovered by Michael Faraday.
Question 7
1 / -0

According to Faraday's law, the total charge induced in a conductor that is moved in a magnetic field depends upon

A
Initial magnetic flux

B
Final magnetic flux

C
Rate of change of magnetic flux

D
Change in magnetic flux

Solution

Answer is D.

Faraday's law of induction is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force.
The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnetic flux enclosed by the circuit.
Question 8
1 / -0

Unit of induced emf is:

A
ampere

B
volt

C
joule

D
electron volt

Solution

Induced emf is potential difference only , hence its unit is volt only.
Question 9
1 / -0

When the current through the electromagnet of a relay reaches a particular value

A
It breaks the circuit

B
It open the circuit by pulling in an iron contact

C
It closes the circuit by pulling in an iron contact

D
Both A or C

Solution

They are ways of switching using a low current to use an electromagnet to close or open a spring steel contact.They are often used to isolate a user from a high voltage that needs to be switched, using low current, low voltage to operate the relay, rather than having a user come in direct proximity to the higher voltage that needs to be switched.When the current through the electromagnet of a relay reaches a particular value it either breaks the circuit by repllening or closes the circuit by pulling in an iron contact.
Question 10
1 / -0

Whenever there is a change in the magnetic flux linked with a closed circuit, an emf and a current are induced in the circuit. This statement is referred to as:

A
Lenz's law

B
Faraday's second law of electromagnetic induction

C
Faraday's first law of electromagnetic induction

D
Laplace's law

Solution

Faraday's first law of electromagnetic induction state that whenever a conductor are placed in a varying magnetic field emf are induced which is called induced emf, if the conductor circuit are closed current are also induced which is called induced current.
So given statement is for Faraday's first law of electromagnetic induction.
Therefore, C is correct option.

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Electromagnetic Induction Test - 19

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Electromagnetic Induction Test - 19

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Question 1

$$0.05 V$$

$$0.5 V$$

$$500 V$$

$$50 V$$

Solution

Question 2

Henry

Tesla

Weber

Gauss

Solution

Question 3

frequency of the AC source is decreased

number of turns in the coil is reduced

a capacitance of reactance $$X_C = X_L$$is included in the same circuit

an iron rod is inserted in the coil

Solution

Question 4

current is always induced

an emf and a current are always induced

an emf is induced but a current is never induced

an emf is always induced and a current is induced when the coil is a closed one

Solution

Question 5

$$N^{0} $$

$$N$$

$$N^{2} $$

$$N^{-2} $$

Solution

Question 6

Lenz

Maxwell

Fleming

Faraday

Solution

Question 7

Initial magnetic flux

Final magnetic flux

Rate of change of magnetic flux

Change in magnetic flux

Solution

Question 8

ampere

volt

joule

electron volt

Solution

Question 9

It breaks the circuit

It open the circuit by pulling in an iron contact

It closes the circuit by pulling in an iron contact

Both A or C

Solution

Question 10

Lenz's law

Faraday's second law of electromagnetic induction

Faraday's first law of electromagnetic induction

Laplace's law

Solution

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