WAEC Physics Past Questions & Answers - Page 89

442.

An atom in an excited state is one whose

A.

potential energy is minimum

B.

potential energy is maximum

C.

electron are in the conduction band

D.

electron have moved to higher energy level

Correct answer is D

No explanation has been provided for this answer.

443.

In a R-C circuit

A.

Irms leads Vrms by 60o

B.

Irms slags Vrms by 60o

C.

Vrms lags Irms by 90o

D.

Vrms leads Irms by 90o

Correct answer is C

No explanation has been provided for this answer.

444.

An inductor is connected to a 24V, 50Hz mains supply. If the current through the inductor is 1.5A, calculate the inductance of the inductor (\(\pi = \frac{22}{7}\))

A.

8.0 x 102H

B.

7.5 x 10oH

C.

1.6 x 10oH

D.

5.1 x 10-2H

Correct answer is D

\(X_L = \frac{V}{I} = \frac{24}{1.5} = 16\Omega\)

L = \(\frac{XL}{2 \pi f} = \frac{16}{2 \pi 50}\)

= 0.05H

445.

Which of the following modes is the most economical method of transmitting electrical power over long distances?

A.

alternating current at low voltage and high current

B.

alternating current at high voltage and high current

C.

alternating current at high voltage and low current

D.

direct current at low voltage and high current

Correct answer is C

No explanation has been provided for this answer.