WAEC Past Questions and Answers - Page 4127

20,631.

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

A.

0.01

B.

0.02

C.

50.00

D.

100.00

E.

200.00

Correct answer is D

No explanation has been provided for this answer.

20,632.

If the current in the resistor R in diagram above is 0.05A, calculate the p.d. across the inductor.

A.

2.5V

B.

25.0V

C.

49.0V

D.

50.0V

E.

250.0V

Correct answer is A

V= i × \(_l\)

X\(_l\) = inductive reactance → 50

I = current → 0.05A
V = 0.05 × 50

V = 2.5volt

20,633.

Calculate the inductive reactance of the circuit shown above.

A.

50.00

B.

5.00

C.

0.50

D.

0.05

E.

0.02

Correct answer is A

No explanation has been provided for this answer.

20,634.

Calculate the electric potential at a distance of 20.0cm from a point charge of 0.015C placed in air of permittivity (Take 1/4πεo as 9.0 x 109 Nm2C2)

A.

3.40x106V

B.

6.75x105V

C.

6.75x1012V

D.

3.40x105V

E.

8.30 x 102V

Correct answer is B

No explanation has been provided for this answer.

20,635.

Calculate the inductance L of the coil in the circuit shown above.

A.

14.4H

B.

3.8H

C.

0.6H

D.

0.4H

E.

0.2H

Correct answer is C

XL = \(\frac{V}{I} = \frac{240}{2} = 120\Omega\)

L = \(\frac{X_L}{2 \pi f}\)

= \(\frac{120 \times \pi}{2 \times \pi \times 100}\)

= 0.6H