A wooden stick of length 3l is rotated about an end with constant angular velocity ω in a uniform magnetic field B perpendicular to the plane of motion. If the upper one third of its length is coated with copper, the potential difference across the whole length of the stick is –

      

1. 9l22                           

2. 4l22

3. 5l22                           

4. l22

Subtopic:  Motional emf |
From NCERT
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A train is moving at a rate of 72 km/hr on a horizontal plane. If the earth's horizontal component of magnetic field is 0.345 A/m and the angle of dip is 30°, then the potential difference across the two ends of a compartment of length 1.7 m will be-

1.  1.7 V                             

2.  853×10-4 V

3.  85×10-4 V                 

4.  850 μ V

Subtopic:  Motional emf |
From NCERT
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An air-plane with 20m wing spread is flying at 250 ms-1 straight south parallel to the earth’s surface. The earth’s magnetic field has a horizontal component of 2 × 105 Wb m2 and the dip angle is 60º. Calculate the induced emf between the plane tips is:

1.  0.174 V                 

2.  0.173 V 

3.  1.173 V                 

4.  0.163 V

Subtopic:  Motional emf |
 77%
From NCERT
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A wire of fixed lengths is wound on a solenoid of length l and radius r. Its self inductance is found to be L. Now if same wire is wound on a solenoid of length l/2 and radius r/2, then the self inductance will be –

1.  2L                     

2.  L 

3.  4L                     

4.  8L

Subtopic:  Self - Inductance |
 52%
From NCERT
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A wire in the form of a circular loop of radius 10 cm lies in a plane normal to a magnetic field of 100 T. If this wire is pulled to take a square shape in the same plane in 0.1 s, average induced emf in the loop is: 

1.  6.70 volt                   

2.  5.80 volt 

3.  6.75 volt                   

4.  5.75 volt

Subtopic:  Faraday's Law & Lenz Law |
 60%
From NCERT
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A superconducting loop of radius R has self inductance L. A uniform and constant magnetic field B is applied perpendicular to the plane of the loop. Initially current in this loop is zero. The loop is rotated by 180°. The current in the loop after rotation is equal to –

1. zero                                 

2. BπR2L

3. 2BπR2L                           

4. BπR22L

Subtopic:  Self - Inductance |
 57%
From NCERT
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A coil of inductance 8.4 mH and resistance 6Ω is connected to a 12 V battery. The current in the coil is 1.0 A at approximately the time. 

1.  500 ms                 

2.  20 ms 

3.  35 ms                   

4.  1 ms

Subtopic:  LR circuit |
 54%
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PQ is an infinite current carrying conductor. AB and CD are smooth conducting rods on which a conductor EF moves with constant velocity v as shown. The force needed to maintain constant speed of EF is –

                    

1. 1VRμ0Iv2π ln ba2                       

2. 1VRμ0Iv2 ln ba2

3. VRμ0IV2 ln ba2                         

4. VRμ0IV2π ln ba2

Subtopic:  Motional emf |
From NCERT
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A 50 turns circular coil has a radius of 3 cms, it is kept in a magnetic field acting normal to the area of the coil. The magnetic field B increased from 0.10 tesla to 0.35 tesla in 2 milliseconds. The average induced emf in the coil is-

1.  1.77 volts                     

2.  17.7 volts 

3.  177 volts                     

4.  0.177 volts

Subtopic:  Faraday's Law & Lenz Law |
 72%
From NCERT
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A semicircular wire of radius R is rotated with constant angular velocity ω about an axis passing through one end and perpendicular to the plane of the wire.

                         

There is a uniform magnetic field of strength B. The induced emf between the ends is -

1. BωR2/2                           

2. 2BωR2

3. is variable                         

4. none of these

Subtopic:  Motional emf |
 65%
From NCERT
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