JAMB Physics Past Questions & Answers - Page 169

841.

The half-life of a radioactive substance is 2 seconds. Calculate the decay constant

A.

0.035s-1

B.

0.151s-1

C.

0.347s-1

D.

0.576s-1

E.

1.386s-1

Correct answer is C

\(\lambda = \frac{0.693}{T_{\frac{1}{2}}} = \frac{0.693}{2}\)

= 0.347s-1

842.

An electron charge 1.6 x 10-19C is accelerated in vacuum from rest at zero volt towards a plate at 40k V. Calculate the kinetic energy of the electron

A.

4.0 x 10-26J

B.

4.0 x 10-21J

C.

6.4 x 10-20J

D.

3.2 x 10-15J

E.

2.5 x 10-20J

Correct answer is D

E = \(\frac{1}{2}QV = \frac{1}{2} \times 1.6 \times 10^{-19} \times 40000\)

= 3.2 x 10-15J

844.

The unit of stress is

A.

Nm

B.

N

C.

Nm-2

D.

Nm2

E.

Nm1

Correct answer is C

No explanation has been provided for this answer.

845.

An induction coil is generally used to?

A.

rectify an alternating current

B.

produce a large input voltage

C.

smoothen a pulsating direct current

D.

modulate an incoming signal

E.

produce a large output voltage

Correct answer is E

An induction coil is a device  used to produce high emf from a low-voltage direct current (DC) supply.