WAEC Past Questions and Answers - Page 3318

16,586.

Which of the following is a unit of the time rate of flow of electric charges?

A.

coulomb

B.

ampere

C.

volt

D.

watt

Correct answer is B

No explanation has been provided for this answer.

16,588.

Two bodies each carrying a charge of 2.00 x 10-10C are 5cm apart. Calculate the magnitude of the force between the charges.[\(\frac{1}{4\pi \mathit{E}_o} = 9.00 \times 10^9 Nm^2C{-2}\)]

A.

1.44 x 10-7N

B.

7.20 x 10-9N

C.

7.20 x 10-11N

D.

1.44 x 1011N

Correct answer is A

f = \(\frac{1}{4 \pi \mathit{E}_o} \times \frac{Q^2}{r^2} = \frac{9 \times 10^9(2 \times 10^{-2})^2}{(0.05)^2}\)

= 1.44 x 10-2N

16,589.

A negatively charged rod is held close to an uncharged metal ball on an insulating stand. The ball will

A.

be negatively charged

B.

be positively charged

C.

have an excess negatively charges on the side nearest the rod

D.

have an excess positively charges on the side nearest the rod

Correct answer is D

No explanation has been provided for this answer.

16,590.

A sound wave is produced fron a source ans an echo is heard t seconds afterwards. If d is the distance of the reflecting surface from the source, v the speed, p the wavelength and T the period of the wave, then

A.

d = \(\frac{2t}{\lambda}\)

B.

d = \(\frac{\lambda t}{2T}\)

C.

d = \(\frac{2T}{\lambda t}\)

D.

d = \(\frac{\lambda T}{2t}\)

Correct answer is B

V = \(\frac{2d}{t}\)

f\(\lambda = \frac{2d}{t} = \frac{\lambda}{T} = \frac{2d}{t}\)