JAMB Physics Past Questions & Answers - Page 431

2,151.

Which of the following statements is true of the properties of a moving coil galvanometer?

A.

THe coil has a small area

B.

There are strong hair springs to gives a large control panlel

C.

There is a strong permanent magnet to give high magnetic flux

D.

it has a small number of turns of coil

Correct answer is C

The galvanometer possesses a rectangular coil mounted on a soft iron core rotating on a magnetic field induced by a permanent magnet.

2,152.

A current of 0.5 A flowing 3h Deposits 2g of metal during electrolysis. The quantity of the same metal that would be deposited by the currents of 1.5A flowing in 1h is

A.

2g

B.

6g

C.

10g

D.

18g

Correct answer is A

From Faradays Law, mass deposited during electrolysis is given by
M = ItZ
=> Z = M/(It)

= __2
0.5x3x60x60

For a current of 1.5A flowing for 1h, the mass M, deposited is given by
M= ZiT
= 2 / (0.5x3x60x60) x 0.5x1x60x60 / 1
= 2.0g
M = 2.0g

2,153.

At what frequency would a capacitor of 2.5μF
used in radio circuit have a resistance of 250Ω

A.

π/800 Hz

B.

800/π Hz

C.

200π Hz

D.

2000π Hz

Correct answer is B

Capacitive Reactance = ___1
2π + C

=> 250 = ____1
2 x π x f x 2.5 x 106

250/1 = 106/5.0xf
=> F = ___106
250 x 5.0 x π

= 106
1250π

800/π

2,154.

The carbon-granules microphone works on the principle of change in

A.

inductance

B.

resistance

C.

capacitance

D.

voltage

Correct answer is B

No explanation has been provided for this answer.

2,155.

A transistor is used in the amplification of signals because it

A.

controls the flow of current

B.

consumes a lot of power

C.

allows doping

D.

contains electron and hole carriers

Correct answer is A

No explanation has been provided for this answer.