WAEC Past Questions and Answers - Page 3508

17,536.

A chemical cell of internal resistance 1\(\Omega\) supplies electric current to an external resistor of resistance 3\(\Omega\). Calculate the efficiency of the cell

A.

75%

B.

50%

C.

33%

D.

25%

Correct answer is A

R = \(r_1 + R = 1 + 3 = 4\Omega\)

\(\frac{3}{4} \times \frac{100}{1} = 75\)%

17,538.

Two capacitors of capacitance 0.4\(\mu F\) and 0.5\(\mu F\) are connected in parallel and charged to a p.d. of 50V, Determine the total charge acquired

A.

45\(\mu C\)

B.

25\(\mu C\)

C.

20\(\mu C\)

D.

10\(\mu C\)

Correct answer is A

C = \(C_1 + C_2\) = 0.4 + 0.5 = 0.9\(\mu F\)

Q = Cv = 0.9 x 50 = 45\(\mu C\)

17,539.

The ability of a material to store an electric charge when its plates are at different potentials is referred to as its

A.

conductance

B.

inductance

C.

capacitance

D.

resistance

Correct answer is C

No explanation has been provided for this answer.

17,540.

In which of the following media is the transmission of sound wave fastest?

A.

Vacuum

B.

Air

C.

Wood

D.

Iron

Correct answer is D

No explanation has been provided for this answer.