WAEC Past Questions and Answers - Page 4027

20,131.

The angle subtended at the centre by a chord of a circle radius 6cm is 120°. Find the length of the chord.

A.

3cm

B.

6cm

C.

\(4\sqrt{2}\) cm

D.

\(3\sqrt{3}\) cm

E.

\(6\sqrt{3}\) cm

Correct answer is E

\(\frac{r}{6} = \sin 60 \)

\(r = 6 \sin 60\)

= \(6 \times \frac{\sqrt{3}}{2}\)

= \(3\sqrt{3}\)

Chord = 2r = \( 2 \times 3\sqrt{3}\)

= \(6\sqrt{3}\)

20,132.

A capacitor of capacitance 25µF is connected to an a.c power source of frequency 200/πHz. Calculate the reactance of the capacitor

A.

0.01Ω

B.

0.02Ω

C.

50Ω

D.

100Ω

E.

150Ω

Correct answer is D

\(X_c=\frac{1}{2\pi{fc}}\)=\(\frac{1}{2\times\pi\times\frac{200}{\pi}\times 25\times 10^{-6}}=\frac{10^6}{10^4}\)=100 Ω

20,133.

A charge of 1 x \(10^{-5}\)C experiences a force of 40N at a certain point in space. What is the magnitude of the electric field intensity at the point in Newton and couloumb

A.

8 x \(10^{6}\)

B.

4 x \(10^{6}\)

C.

3 x \(10^{-4}\)

D.

2 x \(10^{-4}\)

E.

5 x \(10^{-7}\)

Correct answer is B

\(E= \frac{F}{O}= \frac{40}{1\times10^{-5}}=4 \times10^{6}\)

20,134.

The current in a series R-L-C circuit attains its maximum value when the

A.

Impedance is greater than the capacitive reactance

B.

Inductive reactance is equal to the capacitive reactance

C.

Inductive reactance is greater than the capacitive reactance

D.

capacitive reactance is less than resistance

E.

Inductive reactance is greater than the capacitive reactance

Correct answer is B

No explanation has been provided for this answer.