Two tangent galvanometers, which are identical except in their nu

Subject

Physics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

21.

See the diagram. Area of each plate is 2.0 m2 and d = 2 x 10-3 m. A charge of 8.85 x 10-8 C is given to Q. Then the potential of Q becomes

             

  • 13 V

  • 10 V

  • 6.67 V

  • 8.825 V


22.

Three conductors draw currents of 1 A, 2 A and 3 A respectively, when connected in turn across a battery. If they are connected in series and the combination is connected across the same battery, the current drawn will be

  • 611 A

  • 57 A


23.

In the circuit, R1 = R2. The value of E and R1 are (E - EMF, R1 - resistance)

            

  • 180 V, 60 Ω

  • 120 V, 60 Ω

  • 180 V, 10 Ω

  • 120 V, 10 Ω


24.

Masses of three wires of copper are in the ratio of 1 : 3 : 5 and their lengths are in the ratio of 5 : 3 : 1. The ratio of their electrical resistances is

  • 1 : 3 : 5

  • 5 : 3 : 1

  • 1 : 15 : 125

  • 125 : 15 : 1


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25.

For a transformer, the turns ratio is 3 and its efficiency IS 0.75. The current flowing in the primary coil is 2 A and the voltage applied to it is 100 V. Then the voltage and the current flowing in the secondary coil are respectively

  • 150 V, 1.5 A

  • 300 V, 0.5 A

  • 300 V, 1.5 A

  • 150 V, 0.5 A


26.

A proton and helium nucleus are shot into a magnetic field at right angles to the field with same kinetic energy. Then the ratio of their radii is

  • 1 : 1

  • 1 : 2

  • 2 : 1

  • 1 : 4


27.

Two identical circular coils A and B are kept on a horizontal tube side by side without touching each other. If the current in the coil A increases with time, in response, the coil B

  • is attracted by A

  • remains stationary

  • is repelled

  • rotates


28.

In the diagram, I1, I2 are the strength of the currents in the loop and straight conductors respectively. OA = AB = R. The net magnetic field at the centre O is zero. Then the ratio of the currents in the loop and the straight conductors is

                    

  • π

  • 2π

  • 1π

  • 12π


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29.

Two tangent galvanometers, which are identical except in their number of turns, are connected in parallel. The ratio of their resistances of the cols is 1 : 3. If the deflections in the two tangent galvanometers are 30° and 60° respectively, then the ratio of their number of turns is

  • 1 : 1

  • 3 : 1

  • 1 : 3

  • 1 : 6


C.

1 : 3

We know that the current passing through galvanometer coil is

I = K tan θ  where K = 2rBH0 Here, I1 = K1 tan θ1 and I2 = K2 tan θ2or          I1I2 = K1 tan θ1K2 tan θ2 = 2rBHn1μ0 tan θ12rBHn2μ0 tan θ2        R2R1 = n2 tan 30°n1 tan 60°          31 = n2n1  33              I = VR         n1n2 = 13


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30.

A charged particle with a velocity 2 x 103 ms-1 passes undeflected through electric field and magnetic fields in mutually perpendicular directions. The magnetic field is 1.5 T. The magnitude of electric field will be

  • 1.5 × 103 NC-1

  • 2 × 103 NC-1

  • 3 × 103 NC-1

  • 1.33 × 103 NC-1


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