26. What is the self-inductance of a coil which produces 5V when the current changes from 3 ampere to 2 ampere in one millisecond?

1. 1. 5000 henry

   
   
   

   2. 5 milli-henry ​

   
   
   

   3. 50 henry

   
   
   

   4. 5 henry

   
   
   

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1. View Hint View Answer Discuss in Forum

   L =	e
   	di
   	dt

   
   

   =	e dt	=	5 × 10-3	H = 5 mH
   	di		(3 - 2)

   Correct Option: B

   L =	e
   	di
   	dt

   
   

   =	e dt	=	5 × 10-3	H = 5 mH
   	di		(3 - 2)

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27. ​If N is the number of turns in a coil, the value of self inductance varies as​​

1. 1. N⁰

   
   
   

   2. N

   
   
   

   3. N²

   
   
   

   4. N^–2

   
   
   

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1. View Hint View Answer Discuss in Forum

   L =	Nφ	; φ = BA;
   	i

   
   

   B =	μ0Ni
   	2R

   
   

   ⇒ L =	N	=		μ0Ni		A
   	i			2R

   
   

   =	μ0N2	A ⇒ L ∝ N2
   	2R

   Correct Option: C

   L =	Nφ	; φ = BA;
   	i

   
   

   B =	μ0Ni
   	2R

   
   

   ⇒ L =	N	=		μ0Ni		A
   	i			2R

   
   

   =	μ0N2	A ⇒ L ∝ N2
   	2R

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28. A rectangular coil of 20 turns and area of cross-section 25 sq. cm has a resistance of 100Ω. If a magnetic field which is perpendicular to the plane of coil changes at a rate of 1000 teals per second, the current in the coil is

1. 1. 1 A ​

   
   
   

   2. 50 A ​

   
   
   

   3. 0.5 A ​

   
   
   

   4. 5 A

   
   
   

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1. View Hint View Answer Discuss in Forum

   i =	e	=	nAdB/dt
   	R		R

   
   

   =	20 × (25 × 10-4) × 1000	= 0.5 A
   	100

   Correct Option: C

   i =	e	=	nAdB/dt
   	R		R

   
   

   =	20 × (25 × 10-4) × 1000	= 0.5 A
   	100

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29. The total charge induced in a conducting loop when it is moved in a magnetic field depend 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

   q =		idt =	1		edt
   			R

   
   

   =	1			- dφ		dt
   	R			dt

   
   

   =	1		dφ
   	R

   
   (taking only magnitude of e) ​
   Hence, total charge induced in the conducting loop depends upon the total change in magnetic flux.

   Correct Option: C

   q =		idt =	1		edt
   			R

   
   

   =	1			- dφ		dt
   	R			dt

   
   

   =	1		dφ
   	R

   
   (taking only magnitude of e) ​
   Hence, total charge induced in the conducting loop depends upon the total change in magnetic flux.

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30. A 100 millinery coil carries a current of 1A. Energy stored in its magnetic field is​

1. 1. 0.5 J

   
   
   

   2. 1 A

   
   
   

   3. 0.05 J ​

   
   
   

   4. 0.1 J

   
   
   

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1. View Hint View Answer Discuss in Forum

   E =	1	Li2
   	2

   
   

   =	1	× (100 × 10-3) × 12 = 0.05 J
   	2

   Correct Option: C

   E =	1	Li2
   	2

   
   

   =	1	× (100 × 10-3) × 12 = 0.05 J
   	2

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