JAMB Physics Past Questions & Answers - Page 288

1,436.

In A.C circuit theory, the root means square (r.m.s) current, Irms and the peak (maximum)current Io are related by

A.

Io = \(\frac{I_rms}{\sqrt{2}}\)

B.

Irms = \(\frac{I_o}{\sqrt{2}}\)

C.

Irms = \(\frac{\frac{I}{I_o}}{\sqrt2}\)

D.

Irms = \(\frac{I_rms}{\sqrt{2}}\)

Correct answer is B

No explanation has been provided for this answer.

1,437.

In alternating current theory, the units of impedance, r.m.s. voltage and resonance frequency are respectively equal to

A.

volt, ampere and hertz

B.

ohms, volt and hertz

C.

watt, ohms and radian

D.

ohms, hertz and joule

Correct answer is B

No explanation has been provided for this answer.

1,438.
1,439.

The heat produced in a conductor carrying an electric current is

A.

inversely proportional to the current and the resistance

B.

directly proportional to the current, resistance and the time

C.

inversely proportional to of the resistance, current and the time

D.

directly proportional to the square of the current, the resistance and the time

Correct answer is D

No explanation has been provided for this answer.

1,440.

Which of the following apparatus will require the smallest fuse rating for its protection?

A.

60W, 240V

B.

60W, 40V

C.

40W, 12V

D.

40W, 5V

Correct answer is A

I = \(\frac{P}{V}\) = \(\frac{60}{240}\) = 0.25A

I = \(\frac{P}{V}\) = \(\frac{60}{40}\) = 1.5A

I = \(\frac{P}{V}\) = \(\frac{40}{12}\) = 3.3A

I = \(\frac{P}{V}\) = \(\frac{40}{5}\) = 8A