JAMB Physics Past Questions & Answers - Page 284

1,416.

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

Correct answer is C

No explanation has been provided for this answer.

1,417.

How long does it take a 750W heater to raise the temperature of 1kg of water from 20oC to 50oC [specific heat capacity of water = 4200Jkg-1K-1]

A.

84s

B.

112s

C.

168s

D.

280s

Correct answer is C

Heat energy = Elect. energy

mc\(\theta\) = power x time

1 x 4200 x (50 - 20) = 750 x t

t = 168s

1,418.

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? [the specific latent heat of steam is 2,260,000Jkg-1, specific heat capacity of water is 4200Jkg-1K-1]

A.

4200J

B.

2,260,OOOJ

C.

9,040,000J

D.

9,380,000J

Correct answer is C

Heat by water = mc\(\theta\)

Heat by steam = mc\(\theta\) + mL

Difference = mL = 4 x 2,260,000

= 9,040,000J

1,419.

A brass rod is 2m long at a certain temperature. What is the length for a temperature rise of 100K, if the expansivity of brass is 18 x 10-6K-1?

A.

2.0036m

B.

2.0018cm

C.

2.1800

D.

2.0360m

Correct answer is A

\(\alpha\) = \(\frac{L_2 - L_1}{L_1 \times \Delta \theta}\)

18 x 10-6 = \(\frac{L_2 - 2}{2\times 100}\)

L = 2.0036m

1,420.

A thermometer with an arbitrary scale S, of equal division registers -30oS at the ice point and +90oS at the steam point. Calculate the Celsius temperature corresponding to 60oS

A.

25.0oC

B.

50.0oC

C.

66.7oC

D.

75.0oC

Correct answer is D

100oC ... 90oS

\(\theta\)oC ... 60oS

0oC ... 30oS

\(\frac{\theta - 0}{100 - 0}\) = \(\frac{60 - (-30)}{90 - (-30)}\)

\(\theta\) = 75oC