WAEC Physics Past Questions & Answers - Page 257

1,281.

The saturated vapour pressure of a liquid increases as the

A.

volume of the liquid increases

B.

volume of the liquid decreases

C.

temperature of the liquid increases

D.

temperature of the liquid decreases

E.

mass of the liquid decreases

Correct answer is C

No explanation has been provided for this answer.

1,282.

The inside of a vacuum flask is usually coated with silver to reduce heat lost by

A.

convection

B.

conduction

C.

radiation

D.

absorption

E.

evaporation

Correct answer is C

No explanation has been provided for this answer.

1,283.

The heating element in an electric kettle is usually located near the bottom of the kettle because

A.

water is a good conductor of heat

B.

heat can be more quickly radiated to all parts of the water

C.

no heat can be lost to the surroundings

D.

the convectional currents which are set up can carry heat to all parts of the water

E.

the molecules of the heating element can carry heat to all parts of the water.

Correct answer is D

No explanation has been provided for this answer.

1,284.

What is the difference in the amount of heat given out by 4kg of steam and 4kg of water when both are cooled from 100oC to 80oC? (Specific latent heat of steam = 2.260,000J kg-1) (Specific heat capacity of water =4,200 J kg-1)

A.

336,000J

B.

672,000J

C.

8,704,000J

D.

9,040,000J

E.

9,376,000J

Correct answer is C

\(Q_{s} - Q_{w} = (4 \times 2260000) - (4 \times 4200 \times (100 - 80))\)

= \(9040000 - 336000\)

= \(8,704,000 J\)