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.

3,746.

A galvanometer with full-scale deflection of 10 mA is to be converted to a voltmeter with full-scale deflection of 5v.  if a series resistance of 498Ω is used for the conversion, the resistance of the galvanometer is ?

A.

1Ω

B.

2Ω

C.

5Ω

D.

10Ω

Correct answer is B

r = resistance of the galvanometer

l = current through galvanometer = 1mA or 0.01A

V1 = p.d across the galvanometer = I X r = 0.01 X r

: V1 = 0.01r

V2 =  p.d across the  multiplier = 5 - 0.01r


R = resistance of the multiplier = 498Ω
 

where R = \(\frac{V}{I}\) --> 498 = \(\frac{5 - 0.01r}{0.01}\)

CROSS MULTIPLY --> 498 X 0.01 = 5 - 0.01r

0.01r = 5 - 4.98

∴ r = \(\frac{0.02}{0.01}\) = 2Ω

3,747.

Power supply is transmitted at a very high voltage and low current in order to?

A.

make pass through the trasformers

B.

increase the power supply

C.

make it travel fast

D.

prevent overheating of the coil

Correct answer is D

H eat generated in a wire carrying current, H = 12 Rt.
so, when voltage is high and current is low heat generated in the wire will be minimal.
Therefore, high voltage and low current prevent overheating of the coil.

3,748.

When a positively charged rod is brought nearer the cap of a positively charged electroscope, the leaves divergence will?

A.

be induced

B.

converge

C.

diverge

D.

remain constant

Correct answer is C

Since the charged rod is not in contact with the electroscope, the leaves divergence will diverge.

3,749.

Dispersion occurs when white light passes through a glass prism because of the?

A.

different hidden colours in the glass

B.

different speeds of the colour in the glass

C.

defects in the glass

D.

high density of the glass

Correct answer is B

Dispersion is the splitting of white light into its spectral component colors and is caused by different speed of the colors in the prism.

3,750.

Which of the following is used for the correction of short sightedness?

A.

convex lens

B.

concave lens

C.

convex mirror

D.

concave mirror

Correct answer is B

Concave lens diverges parallel rays of light. A short sighted person has the image formed before the retina,and the rays have to be diverged so that they intersect to form image onto the retina