A long solenoid having 1000 turns per cm is carrying alternating current of one ampere peak value. A search coil of area of cross-section 1×10-4 m2 and of 20 turns is placed in the middle of the solenoid so that its plane is perpendicular to the axis of the solenoid. The search coil registers a peak voltage 2.5×10-2 V. The frequency of the current in the solenoid is -

1.  1.6 per second                   

2.  0.16 per second

3.  15.9 per second                 

4.  15.85 per second

Subtopic:  Faraday's Law & Lenz Law |
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A coil of the area 7 cm2 and of 50 turns is kept with its plane normal to a magnetic field B. A resistance of 30 ohms is connected to the resistance-less coil. B is 75e-200t Gauss. The current passing through the resistance at t = 5 ms will be-

1.  0.64 mA                     

2.  1.05 mA 

3.  1.75 mA                     

4.  2.60 mA

Subtopic:  Faraday's Law & Lenz Law |
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Assertion: When a coil is joined to a cell, the current through the cell will be 10% less than its steady-state value at time t =τ loge 10, where τ is the time constant of the circuit.

Reason: When a coil is joined to a cell, the growth of current is given by i=i0e-t/τ

  1. If both the assertion and the reason are true and the reason is a correct explanation of the assertion
  2. If both the assertion and reason are true but the reason is not a correct explanation of the assertion
  3. If the assertion is true but the reason is false
  4. If both the assertion and reason are false
Subtopic:  LR circuit |
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Assertion: The magnetic flux linked with a coil is ϕ, and the emf induced in it is ε. If ϕ=0, ε must be zero.

Reason : ε=-dt        ε=0  when ϕ=0

(a) Assertion and Reason both are correct and the Reason is the correct explanation of the Assertion.

(b) Assertion and Reason both are correct but the Reason is not the correct explanation of the Assertion.

(c) The assertion is correct but the Reason is wrong.

(d) Assertion and Reason both are wrong.

Subtopic:  Faraday's Law & Lenz Law |
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Assertion : The coil in the resistance boxes are made by doubling the wire.

Reason : Thick wire is required in resistance box.

  1. If both the assertion and the reason are true and the reason is a correct explanation of the assertion
  2. If both the assertion and reason are true but the reason is not a correct explanation of the assertion
  3. If the assertion is true but the reason is false
  4. If both the assertion and reason are false
Subtopic:  Self - Inductance |
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Rate of increment of energy in an inductor with time in series LR circuit getting charge with battery of emf E is best represented by – [inductor has initially zero current]

1.                        

2. 

 

3.                        

4. 

Subtopic:  LR circuit |
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A copper rod of length 0.19 m is moving parallel to a long wire with a uniform velocity of 10 m/s. The long wire carries 5 ampere current and is perpendicular to the rod. The ends of the rod are at distances 0.01 m and 0.2 m from the wire. The emf induced in the rod will be-

1.  10 μV                           

2.  20 μV

3.  30 μV                           

4.  40 μV

Subtopic:  Motional emf |
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The magnetic flux through each turn of a 100 turn coil is t3  2t × 10-3 Wb, where t is in second. The induced emf at t = 2 s is

1. -4 V                       

2. -1 V

3. +1 V                       

4. +4 V

Subtopic:  Faraday's Law & Lenz Law |
 74%
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Loop A of radius (r << R) moves towards loop B with a constant velocity v in such a way that their planes are always parallel.

                       

What is the distance (x) between the two loops when the induced emf in loop A is maximum –

1. R                                     

2. R2

3. R2                                     

4. R1-12

Subtopic:  Motional emf |
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The inductance of a closed-packed coil of 400 turns is 8 mH. A current of 5 mA is passed through it. The magnetic flux through each turn of the coil is approximately-

1.  0.1 μ0 Wb                     

2.  0.2 μ0 Wb

3.  1.0 μ0 Wb                     

4.  2.0 μ0 Wb

Subtopic:  Self - Inductance |
 67%
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