WAEC Physics Past Questions & Answers - Page 108

536.

Oxidation of the filament in a light bulb is prevented by the introduction of

A.

hydrogen

B.

oxygen

C.

argon

D.

mercury vapour

Correct answer is C

No explanation has been provided for this answer.

537.

An electron moves with a speed of 2.0 x 106ms-1 in a straight line. Calculate the wave length of the electron wave. [mass of an electron = 9.1 x 10-31 kg][Planck's constant = 6.6 x 10-34Js]

A.

3.63 x 10-19m

B.

6.51 x 10-9m

C.

4.24 x 10-8m

D.

7.25 x 10-8m

Correct answer is C

\(\lambda = \frac{hc}{\frac{1}{2}mv^2} = \frac{6.6 \times 10^{-38} \times 3 \times 10^8}{\frac{1}{2} \times 9.1 \times 10^{-31} (2 \times 10^6)^2}\)

= 4.24 x 10-8m

539.

The energy, E stored in an inductor of inductance L when current I passes through it is given by the equation

A.

E = \(\frac{1}{2} LI^2\)

B.

E = LI2

C.

E \(\frac{1}{2}LI\)

D.

E = \(\frac{1}{2} L^2I\)

Correct answer is B

No explanation has been provided for this answer.

540.

In order to prevent bar magnets from losing their strength, they are stored wih keepers such that the two bars are placed with

A.

like poles facing each other and the keepers placed between them

B.

like poles facing each other and the keepers placed between them

C.

unlike poles facing each other and the keepers placed at their ends

D.

unlike poles facing each other and the keepers placed between them

Correct answer is C

No explanation has been provided for this answer.