JAMB Physics Past Questions & Answers - Page 229

1,141.

Which of the following methods CANNOT be used to produce a steel magnet? The

A.

passing of an electric current through a solenoid

B.

repeated stroking of the specimen with a magnet

C.

repeated stroking of the specimen in opposite directions with magnets

D.

heating of the specimen

E.

hammering of the specimen in the earth's magnetic field

Correct answer is D

No explanation has been provided for this answer.

1,142.

If the distance between two stationary charged particle is doubled, the magnitude of the electro-static force between them will be

A.

doubled

B.

halved

C.

a quarter of its former value

D.

unchanged

E.

four times the original value

Correct answer is C

F \(\alpha\) \(\frac{1}{d^2}\)

F x d2 = constant

F1 x (d1)2 = F2 x (d2)2

d2 = 2d1

F1 x (d1)2 = F2 x (2d1)2

F2 = \(\frac{1}{4}\)F1

1,143.

A charge of one coulomb liberates 0.0033g of copper in an electrolytic process. How long will it take a current of 2A to librate 1.98g of copper in such a process?

A.

5 mins

B.

30 mins

C.

50 mins

D.

60 mins

E.

120 mins

Correct answer is A

0.0033g = 1 coulomb

1.98gs = 1.98 x 1

= 600 cou.

Q = It

600 = 2 x t

t = 300sec = 5 mins

1,144.

A narrow beam of white light can be split up into different colours by a glass prism. The correct explanation is that

A.

white light is an electromagnetic wave

B.

the prism has all the colours of the white light

C.

white light has undergone total internal reflection in the prism

D.

different colours of white light travel with different speeds in glass

E.

white ligth consist of yellow, green and red colours

Correct answer is D

No explanation has been provided for this answer.

1,145.

Two rays of light from a point below the surface of water are equally inclined to each other at 60o in water. What is the angle between the rays when they emerge into air? (Take the refractive index of water to be \(\frac{4}{3}\))

A.

41.8o

B.

44.1o

C.

60.0o

D.

83.6o

E.

120.0o

Correct answer is D

\(\frac{4}{3}\) = \(\frac{sin r_1}{sin 30}\) and \(\frac{4}{3}\) = \(\frac{sin r_2}{sin 30}\)

r1 = 41.8o and r2 = 41.8o

angle between them = r1 + r2

= 83.6o