A straight horizontal wire AB of length l falls from rest under gravity. A uniform horizontal magnetic field B acts perpendicular to the plane of motion of AB, as shown in the figure. The induced emf across AB,  E, is proportional to:
               
1. B 2. l
3. time, t 4. all of the above
Subtopic:  Motional emf |
 84%
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A rod of length l rotates with a uniform angular velocity ω about its perpendicular bisector. A uniform magnetic field B exists parallel to the axis of rotation. The potential difference between the two ends of the rod is:
1. zero
2. 12Blω2
3. Blω2
4. 2Blω2

Subtopic:  Motional emf |
 61%
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A conducting rod is moved with a constant velocity v in a magnetic field. A potential difference appears across the two ends:

(a)  if vl (b)  if vB
(c)  if lB (d)  none of these


Choose the correct option from the given ones:

1. (a) and (b) only
2. (b) and (c) only
3. (d) only
4. (a) and (d) only
Subtopic:  Motional emf |
 80%
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A wheel with 10 metallic spokes each 0.5 m long is rotated with a speed of 120 rev/min in a plane normal to the horizontal component of Earth’s magnetic field HE at a place. If HE=0.4 G at the place, what is the induced emf between the axle and the rim of the wheel? ((1 G=104 T) 
1. 5.12×105 V 
2. 0
3. 3.33×105 V
4. 6.28×105 V

Subtopic:  Motional emf |
 66%
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An L-shaped rod (ABC;AB=BC=a) moves in its own plane with a velocity v parallel to AB. There is a uniform magnetic field B acting into the plane as shown. The emf developed between A,C is:
                            
1. Bav
2. 2Bav
3. Bav2
4. zero
Subtopic:  Motional emf |
 57%
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A conducting circular wire of radius r is moving with constant velocity v towards the right in a uniform magnetic field B. We consider two points X,Y such that chord XY is perpendicular to the velocity v and is at a distance x from the centre (O) of the circle. The EMF induced between X,Y is ε. Then, ε is proportional to:
                
1. x
2. r2x2
3. r
4. xr2x2
Subtopic:  Motional emf |
 73%
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A straight horizontal wire of mass m and length l, and having a negligible resistance can slide freely on a pair of conducting parallel rails, placed vertically. The rails are connected at the top by a capacitor C. A uniform magnetic field B exists in the region, perpendicular to the plane of the rails. The wire:
           
1. falls with uniform velocity.
2. accelerates down with acceleration less than g.
3. accelerates down with acceleration equal to g.
4. moves down and eventually comes to rest.
Subtopic:  Motional emf |
 71%
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A triangular wire frame, in the form of an equilateral triangle PQR moves with a uniform velocity into a region where there is a uniform magnetic field B. The edge PQ is parallel to the boundary of the region and the velocity v is perpendicular to it. The emf(E) induced within the frame is plotted as a function of time t, starting from when the frame enters the magnetic field. E is given by:
1. Bv2t 2. 2Bv2t
3. 32Bv2t 4. 23Bv2t
Subtopic:  Motional emf |
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A rod XY of length l is placed in a uniform magnetic field B, as shown in the diagram. The rod moves with a velocity v, making an angle of 60 with its length. The emf induced in the rod is:
            
1. vBl    2. vBl2   
3. 32vBl 4. 13vBl
Subtopic:  Motional emf |
 73%
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An emf is generated by an ac generator having 100 turn coil, of loop area 1 m2. The coil rotates at a speed of one revolution per second and placed in a uniform magnetic field of 0.05 T perpendicular to the axis of rotation of the coil. The maximum value of emf is:
1. 3.14 V
2. 31.4 V
3. 62.8 V
4. 6.28 V
Subtopic:  Motional emf |
 75%
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