JAMB Physics Past Questions & Answers - Page 265

1,322.

The resistance of a 5m uniform wire of cross-sectional area 0.2 x 10-6m2 is 0.425. What is the resistivity of the material of the wire?

A.

1.10 x 10-6\(\Omega\)m

B.

4.25 x 10-6\(\Omega\)m

C.

2.40 x 10-7\(\Omega\)m

D.

1.70 x 10-8\(\Omega\)m

Correct answer is D

Resistance = \(\frac{\text{ Resistivity x Area}}{Area}\)

= 0.425 x 0.2 x 10-6

= 1.7 x 10-8\(\Omega\)m

1,323.

A bar magnet is most effectively demagnetized by

A.

placing it in a N - 5 position and hitting it with a hammer

B.

subjecting it to an electric current from a battery

C.

bringing its north pole in contact with the north pole of a very strong magnet

D.

heating the magnet

Correct answer is A

No explanation has been provided for this answer.

1,324.

When a number of identical small magnets are arranged in a line, the strength of the resultant magnet

A.

is largest when they are arranged end to end

B.

is greatest when they are arrangedparallel with like poles adjacent to each other

C.

depends only on the number of magnets provided they arev parallel

D.

is greater when the magnets are arranged on a wooden surface than on a metaln surface

Correct answer is A

No explanation has been provided for this answer.

1,325.

Two insulated charged spheres of different sizes and carrying opposite charges are connected together by a metallic conductor. Current will flow from one sphere to the other until both sphere

A.

carry the same magnitude and sign of charge

B.

are at the same potential

C.

are at the same temperature

D.

are of the same size

Correct answer is B

No explanation has been provided for this answer.