Tag: physics

Questions Related to physics

An electron having kinetic energy T is moving in a circular orbit of radius R perpendicular to a uniform magnetic induction $\vec { \mathrm { B } }$  If kinetic energy is doubled and magnetic induction tripled, the radius will

mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

  1. $\frac { 3 R } { 2 }$

  2. $ \frac{{\sqrt 2 }}{3}R$

  3. $\sqrt { \frac { 2 } { 9 } } R$

  4. $\sqrt { \frac { 4 } { 3 } } R$

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Correct Option: B
Explanation:

We know$,$

$R = \frac{{\sqrt {2mk} }}{{qB}}$
$R' = \frac{{\sqrt {2m2k} }}{{q\left( {3B} \right)}}$
$ = \frac{{\sqrt 2 }}{3}\frac{{\sqrt {2mk} }}{{qB}}$
$ = \frac{{\sqrt 2 }}{3}R$
Hence,
option $(B)$ is correct answer.

An average induced emf of 0.4 V appears in a coil when the current in it is changed from 10 A in one direction to 10 A in opposite direction in 0.5 sec. self-inductance of the coil is.

mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

  1. 0.008H

  2. 50 H

  3. 75 H

  4. 100 H

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Correct Option: A

At any instant t currenetI thorugh a coil of sself inductance 2mH is given.The induced e.m.f will be zero at time    

mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

  1. 1 sec

  2. 2 sec

  3. 3 sec

  4. 4 sec

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Correct Option: B

When a current of 5 A flows in the primary coil then the flux linked with the secondary coil is 200 weber. The value of coefficient of mutual induction will be

mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

  1. 1000 H

  2. 40 H

  3. 195 H

  4. 205 H

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Correct Option: B
Explanation:

Coefficient of mutual induction will be the ratio of the flux linked with the secondary coil and the current primary coil.


$ M = \dfrac{200}{5} = 40 H $ 

A cylindrical magnet is kept along the axis of a circular coil. On rotating the magnet about its axis. the coil will have induced in it

mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

  1. No current

  2. A current

  3. Only an e.m.f.

  4. Both an e.m.f. and a current

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Correct Option: A

A coil of insulating wire is connected to battery. If it is moved towards a galvanometer then its point gets deflected because

mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

  1. the coil behaves like a magnet

  2. induced current is produced in the coil

  3. the number of turns in the galvanometer coil remains constant

  4. none of the above

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Correct Option: B
Explanation:

Upon connecting to the battery , a current starts to flow in the insulated wire. This current induces a current in the galvanometer coil  due to mutual  inductance because of the flux linkages. This induced current causes a deflection in the galvanometer . 

Two coils P and Q are lying parallels and very close to each other. Coil P is connected to an AC source whereas Q is connected to a sensitive galvanometer. On pressing key K

mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

  1. small variations are observed in the galvanometer for applied 50 Hz voltage

  2. deflections in the galvanometer can be observed for applied voltage of 1 Hz to 2 Hz.

  3. no deflection in the galvanometer will be observed

  4. constant deflection will be observed in the galvanometer for 50 Hz supply voltage

Show answer
Correct Option: B
Explanation:

Upon connecting to the AC source , a current starts to flow in the coil P. This current induces a current in the galvanometer coil Q due to mutual  inductance because of the flux linkages. This induced current causes a deflection in the galvanometer.

The value of mutual inductance can be increased by

mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

  1. decreasing N

  2. increasing N

  3. winding the coil on wooden frame

  4. winding the coil on china clay

Show answer
Correct Option: B
Explanation:

$M = \mu N _1 N _2 \dfrac{ Area _{12}}{length _{12}} $


$ Area _{12} $ - area in common to both the coils where the flux links both of them together.
$length _{12}$ - length in common to both the coils where the flux links both of them together.
Therefore to increase the mutual inductance, the number of turns can be increased.  

A long straight wire is placed along the axis of a circular ring of radius R. Then mutual inductance of this system is 

mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

  1. $\frac{\mu _{0}R}{2}$

  2. $\frac{\mu _{0}\pi R}{2}$

  3. $\frac{\mu _{0}}{2}$

  4. 0

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Correct Option: D

A coil of wire has 0.2 m radius and 500 turns. It carries a current of 1 A.The magnetic induction at the centre of the coil is 

mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

  1. $1.5\times { 10 }^{ -3 }T$

  2. $1.6\times { 10 }^{ -3 }T$

  3. $1.7\times { 10 }^{ -3 }T$

  4. $1.8\times { 10 }^{ -3 }T$

Show answer
Correct Option: B