Physics – Class 12 Practice Test 6

1. Identify the type of commercial motor which works as a consequence of eddy currents.

Compressors

Turbines

Induction motors

Hydropowered motors

2. Determine the rms value of current in the circuit if a 50 Ω resistor is connected across an ac source of 200 V, 50 Hz?

50 A

1 A

200 A

4 A

3. At what frequency will a coil, which has an inductance of 2.5 H, have a reactance of 3500 Ω?

700Hz

350 Hz

223 Hz

200 Hz

4. What is the magnitude of the force on a current carrying conductor of length L in a perpendicular magnetic field B?

F=I² lB

F=\(\frac {I}{lB}\)

F=IlB²

F=IlB

5. What is the reactance of an inductor in a dc circuit?

Indefinite

Maximum

Minimum

Zero

6. A 1.50 μF capacitor is connected to a 220 V, 50 Hz source. If the frequency is doubled, what happens to the capacitive reactance?

Doubled

Halved

Becomes zero

Remains the same

7. What is the ratio of the speed of infrared and ultraviolet rays in a vacuum?

1:5

2:1

8. Which of the following is usually taken to make the core of a transformer?

Hard iron

Aluminum

Soft iron

Copper

9. Find out the rms value of current in the circuit wherein a 35 mH inductor is connected to 200 V, 70 Hz ac supply.

20 A

15 A

45 A

13 A

10. Identify the expression of Ampere-Maxwell’s Circuital law.

∮\( \overset{\rightharpoonup}{B}.\overset{\rightharpoonup}{dl}\) = μ₀ (I_C I_D)

∮\( \overset{\rightharpoonup}{B}.\overset{\rightharpoonup}{dl}\) = μ₀ (I_C-I_D)

∮\( \overset{\rightharpoonup}{B}.\overset{\rightharpoonup}{dl}\) = μ₀ (I_D-I_C)

∮\( \overset{\rightharpoonup}{B}.\overset{\rightharpoonup}{dl}\) = μ₀ (I_C+I_D)