31. ​If the number of turns per unit length of a coil of solenoid is doubled, the self-inductance of the solenoid will​​

1. 1. ​remain unchanged ​

   
   
   

   2. be halved

   
   
   

   3. ​be doubled ​

   
   
   

   4. become four times

   
   
   

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1. View Hint View Answer Discuss in Forum

   Self inductance of a solenoid
   

   =	μn2A
   	ℓ

   
   So, self induction ∝ n²
   So, inductance becomes 4 times when n is doubled.

   Correct Option: D

   Self inductance of a solenoid
   

   =	μn2A
   	ℓ

   
   So, self induction ∝ n²
   So, inductance becomes 4 times when n is doubled.

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32. An induct or may store energy in

1. 1. ​its electric field

   
   
   

   2. its coils ​

   
   
   

   3. ​its magnetic field

   
   
   

   4. both in electric and magnetic fields

   
   
   

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1. View Hint View Answer Discuss in Forum

   An induct or stores energy in its magnetic field.

   Correct Option: C

   An induct or stores energy in its magnetic field.

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33. The total charge induced in a conducting loop when it is moved in a magnetic field depends on

1. 1. the rate of change of magnetic flux ​

   
   
   

   2. ​initial magnetic flux only ​

   
   
   

   3. the total change in magnetic flux

   
   
   

   4. ​final magnetic flux only

   
   
   

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1. View Hint View Answer Discuss in Forum

   e =	dφ	;
   	dt

   
   

   i =	e	=	1		dφ
   	R		R		dt

   
   Total charge induced
   

   	i dt =		1		dφ	.dt
   			R		dt

   
   

   =	1		φ2	dφ
   	R		φ1

   
   

   =	1	(φ2 - φ1)
   	R

   Correct Option: C

   e =	dφ	;
   	dt

   
   

   i =	e	=	1		dφ
   	R		R		dt

   
   Total charge induced
   

   	i dt =		1		dφ	.dt
   			R		dt

   
   

   =	1		φ2	dφ
   	R		φ1

   
   

   =	1	(φ2 - φ1)
   	R

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