WAEC Past Questions and Answers - Page 3507

17,531.

Lenz's law of electromagnetic induction states that

A.

a force is exerted on a current-carrying conductor in a magnetic field

B.

electromotive force id induced in a circuit whenever there is a change in the magnetic flux linked with the circuit

C.

the magnitude of the induced electromotive force in a circuit is proportional to the rate of change of flux linking the circuit

D.

the induced current in a coil is in such a direction that it sets up a magnetic field which opposes the change producing it

Correct answer is D

No explanation has been provided for this answer.

17,534.

Which of the following statements explains lost volt in an electric circuit? The

A.

total p.d from a source to maintain a flow of current through the circuit as well as the source

B.

p.d to drive current through the circuit component except the source

C.

p.d across all external components connected to the source of electricity

D.

p.d across the internal resistance of the cell

Correct answer is D

The lostvolt is the potential drop in a cell due to internal resistance.

17,535.

An electric lamp is rated 240V, 40W. What is the cost of running the lamp for 72 hours if the electricity authority charges N2.50 per kWh?

A.

N7.20

B.

N18.00

C.

180.00

D.

N720.00

Correct answer is A

Cost = \(\frac{Pt}{1000}\) x cost per kWh

= \(\frac{40 \times 72}{1000} \times 2.50 = N7.20\)