A rod of length l rotates with uniform angular velocity ω about an axis passing through its one end and perpendicular to its length. If a uniform magnetic field exists perpendicular to the axis of rotation, then induced emf across the two ends of the rod is :

1. 12Bωl2

2. Bωl2

3. 2 Bωl2

4. zero

Concept Questions :-

Motional emf
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Energy stored in an inductor can be made four times when

1. inductance is doubled

2. Current is made 2 times

3. current is doubled

4. can never to be made

Concept Questions :-

Self-inductance
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A coil wire of a certain radius has 600 turns and a self-inductance of 36 mH. The self-inductance of a second similar coil of 500 turns will be

1.  25 mH

2.  50mH

3.  108mH

4.  75mH

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The current passing through a choke coil of 5 H is decreasing at the rate of 3 As-1. The emf induced in the coil is 

1. 15 V

2. -15 V

3. 53V

4. -53V

Concept Questions :-

Self-inductance
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If all linear dimensions of an inductor are tripled, then self-inductance will become (keeping the total number of turns per unit length constant)

1.  3 times

2.  9 times

3.  27 times

4. 1/3 times

Concept Questions :-

Self-inductance
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A coil of resistance 20Ω and inductance 5H has been connected to a 200 V battery. The maximum energy stored in the coil is

(1) 250 J

(2) 125 J

(3) 500 J

(4) 100 J

Concept Questions :-

Self-inductance
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A coil has, 1,000 turns and 500 cm2 as its area. The plane of the coil is placed at right angles to a magnetic induction field of 2×10-5 Wb/m2. The coil is rotated through 180° in 0.2. The average e.m.f. induced in the coil, in milli-volts, is

(1) 5

(2) 10

(3) 15

(4) 20

Concept Questions :-

Faraday 's law and lenz law
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The network shown in the figure is part of a complete circuit. If at a certain instant, the current I is 5 Amp and it is decreasing at a rate of 5×103 A/s, then VB-VA is equal to 

1. 20 V

2. 15 V

3. 10 V

4. 5 V

Concept Questions :-

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A small square loop of wire of side l is placed inside a large square of wire of side L (L>>l). The loops are co-planar and their centres coincide. The mutual inductance of the system is proportional to :

1. l/L

2. l2/L

3. L/l

4. L2/l

 

Concept Questions :-

Mutual-inductance
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The key K is inserted at time t= 0. The initial (t=0) and final t currents through battery are :

1. 115Amp, 110Amp

2. 110Amp, 115Amp

3. 215Amp, 110Amp

4. 115Amp, 225Amp

Concept Questions :-

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