Physics questions and answers

Physics Questions and Answers

If you want to learn more about the nature and properties of matter and energy or you're simply preparing for a Physics exam, these Physics past questions and answers are ideal for you.

1,571.

An inductor is connected to a 24V, 50Hz mains supply. If the current through the inductor is 1.5A, calculate the inductance of the inductor (\(\pi = \frac{22}{7}\))

A.

8.0 x 102H

B.

7.5 x 10oH

C.

1.6 x 10oH

D.

5.1 x 10-2H

Correct answer is D

\(X_L = \frac{V}{I} = \frac{24}{1.5} = 16\Omega\)

L = \(\frac{XL}{2 \pi f} = \frac{16}{2 \pi 50}\)

= 0.05H

1,572.

Which of the following modes is the most economical method of transmitting electrical power over long distances?

A.

alternating current at low voltage and high current

B.

alternating current at high voltage and high current

C.

alternating current at high voltage and low current

D.

direct current at low voltage and high current

Correct answer is C

No explanation has been provided for this answer.

1,573.

The core of a transformer is usually laminated in order to

A.

reduce magnetic leakage

B.

reduce eddy current

C.

prevent vibration of the transformer

D.

make magnetic reversal in the core much easier

Correct answer is B

No explanation has been provided for this answer.

1,574.

The magnetic relay is a device used for

A.

timing in sports

B.

storing magnetic field

C.

reading the magnitude of magnetic flux

D.

controlling another circuit carrying larger current

Correct answer is D

No explanation has been provided for this answer.

1,575.

A 12\(\Omega\) resistor dissipates 8kJ of heat in 20s. Calculate the current through the resistor

A.

5.8A

B.

6.9A

C.

30.0A

D.

33.3A

Correct answer is A

Q = I2Rt

I = \(\sqrt{\frac{Q}{Rt}}\)

= \(\sqrt{\frac{8000}{12 \times 20}}\)

= 5.8