JAMB Physics Past Questions & Answers - Page 327

1,631.

Electricity is supplied to a school along a cable of total resistance 0.5Ω with the maximum current drawn from the mains as 100A. The maximum energy dissipated as heat for 1 hr is

A.

3.6 x 103J

B.

5.0 x 103J

C.

3.0 x 105J

D.

1.8 x 107J

Correct answer is D

Elect. energy = I2Rt

= 100 x 100 x 0.5 x 3600

= 1.8 x 107J

1,632.

The iron core of an induction coil is made from bundles of wire so as to

A.

minimize eddy-currents

B.

generate eddy-current

C.

prevent sparking at the contact breaker

D.

get the greatest posible secondary voltage

Correct answer is A

No explanation has been provided for this answer.

1,633.

A parallel plate capacitor has a common plate area of 5 x 10\(^{-8}\)m2 and plate separation of 2 x 10\(^3\)m, Assuming free space,

What is the capacitance? [\(\varepsilon\)o = 9.0 X 10-\(^{-12}\)C2N-1m-2]

A.

2.25 x 10-17F

B.

4.50 x 10-17F

C.

2.25 x 10-16F

D.

4.50 x 10-16F

Correct answer is A

C = \(\frac{{\varepsilon}_oA}{d}\)

= \(\frac{5{\times} 10^{-8} {\times} 10^{-12}{\times} 9}{2 {\times}10^{-3}}\)

= 22.5 x 10-17F

1,634.
1,635.

Which of the following can be used to reduce local action in a Laclanche cell?

A.

A carbon rod as the positive pole

B.

Pure zinc as the negative pole

C.

Potassium permanganate solution in contact with the positive pole

D.

common salt solution

Correct answer is C

No explanation has been provided for this answer.