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JAMB Physics Past Questions & Answers - Page 274

1,366.

The electrochemical equivalent of platinum is 5.0 x 10-7kgC-1 to plate-out 1.0kg of platinum, a current of 100A must be passed through an appropriate vessel for

A.

5.6 hours

B.

56 hours

C.

1.4 x 104 hours

D.

2.0 x 104 hours

Correct answer is A

m = Itz

1 = 100 x 5 x 10-7 x t

t = 20,000sec

= 5.6hrs

1,367.

If a current carrying coil is mounted on a metal frame, the back e.m.f. induced in the coil causes

A.

inductance

B.

eddy currents

C.

elecro-magnetism

D.

dipole moment

Correct answer is B

No explanation has been provided for this answer.

1,368.

To convert an alternating current dynamo into a direct current dynamo, the

A.

number of turns in the coil is increased

B.

strength of the field magnet is increased

C.

slip rings are replaced with a split ring commutator

D.

coil is wound on a soft iron armature

Correct answer is C

No explanation has been provided for this answer.

1,369.

An equipment whose power is 1500W and resistance is 375 ohms would draw a current of

A.

0.10A

B.

2.00A

C.

4.00A

D.

77.5A

Correct answer is B

P = I2R I = PR

I = 1500375

= 2A

1,370.

Which of the following obeys Ohm's Law?

A.

Glass

B.

Diode

C.

All electrolytes

D.

All metals

Correct answer is D

No explanation has been provided for this answer.