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.

541.

A transformer connected to a 240\(V_{r.m.s}\) has 3000 turns in its primary coil and 500 turns in its secondary coil. Calculate the output voltage.

A.

4000V

B.

400V

C.

40V

D.

4V

Correct answer is C

\(N_{p} = 3000 turns\)

\(N_{s} = 500 turns\)

\(E_{p} = 240V_{r.m.s}\)

\(E_{s} = ?\)

\(\frac{N_{s}}{N_{p}} = \frac{E_{s}}{E_{p}}\)

\(\frac{500}{3000} = \frac{E_{s}}{240}\) 

\(\implies E_{s} = \frac{240\times500}{3000} = 40V\)

544.

A circuit is set up as shown in the diagram above. When the key is closed, the ammeter reading will be

A.

6A

B.

4A

C.

2A

D.

1A

Correct answer is C

The resistors are connected both in parallel and series. To calculate the total resistance, we have:

For the parallel connection: \(\frac{1}{R} = \frac{1}{1} + \frac{1}{1}\)

\(\frac{1}{R} = 2 \implies R = 0.5\Omega\)

For the series connection: \(R_{total} = (1 + 0.5)\Omega = 1.5\Omega\)

Recall, \(V=IR\)

\(3 = 1.5I  \implies I = \frac{3}{1.5} =2A\)

545.

Which of the following objects is not a conductor of electricity?

A.

The Earth

B.

Human body

C.

Iron rod

D.

Dry wood

Correct answer is D

Dry wood is rather an insulator and not a conductor.