WAEC Physics Past Questions & Answers - Page 137

681.

Five 80-W and three 100W are run for 8 hours. If the cost of energy is N5.00 per unit, calculate the cost of running the lamp. [1 unit = 1 kW]

A.

N280.00

B.

N28.00

C.

N7.20

D.

N1.44

Correct answer is B

P = (80 x 5 + 100 x 3)8

= 5600W

Cost = \(\frac{5600}{1000} \times 5 = N28\)

682.

A bulb marked 240V, 40W is used for 30 minutes. Calculate the heat generated

A.

320J

B.

400J

C.

10800J

D.

72000J

Correct answer is D

W = P x t

= 40 x 30 x 60

= 72000J

683.

Which of the following operations does not represent an action of a force field?

A.

falling of a mango fruit from the tree

B.

picking of nails using a bar magnet

C.

repulsion of two like charges

D.

pushing of a wheel-barrow on a level gound

Correct answer is D

No explanation has been provided for this answer.

684.

Which of the following components is used for storing electric charges?

A.

inductor

B.

resistor

C.

capacitor

D.

electrometer

Correct answer is C

No explanation has been provided for this answer.

685.

Which of the following statements is correct about resonance? Resonance occurs when a body

A.

vibrates with its natural frequency

B.

is forced to vibrate on its own natural frequency by another body at the same vibration

C.

vibrates at the frquency of the body causing the vibration

D.

vibrates with an irregular frequency

Correct answer is C

No explanation has been provided for this answer.