JAMB Physics Past Questions & Answers - Page 234

1,166.

Which of the following will convert a milliammeter to a voltmeter?

A.

low series resistance

B.

low parallel resistance

C.

high series resistance

D.

high parallel resistance

E.

parallel resistance equal to milliammeter resistance

Correct answer is C

No explanation has been provided for this answer.

1,167.

A cell gives a current of 0.15A through a resistance of 8\(\Omega\) and 0.3A. When the resistance is changed to 3\(\Omega\) the internal resistance of the cell is

A.

0.05\(\Omega\)

B.

1.00\(\Omega\)

C.

1.50\(\Omega\)

D.

2.00\(\Omega\)

E.

2.50\(\Omega\)

Correct answer is D

The E.M.F of a circuit is given by 

\(E=I(R+r)\)

Hence, E = 0.15(8+r)  = 0.3(3+r)

1.2 + 0.15r = 0.9 + 0.3r

1.2 - 0.9 = 0.3r - 0.15r

0.3 = 0.15r

r = \(\frac{0.3}{0.15}\)

r = 2\(\Omega\)

1,168.

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.

1,169.

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

1,170.

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