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JAMB Physics Past Questions & Answers - Page 278

1,386.

The absolute temperature of a perfect gas is proportional to the average

A.

potential energy of the molecules

B.

seperation between the molecules

C.

kinetic energy of the molecules

D.

velocity of the molecules

Correct answer is C

No explanation has been provided for this answer.

1,387.

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

mcθ = power x time

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

t = 168s

1,388.

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 = mcθ

Heat by steam = mcθ + mL

Difference = mL = 4 x 2,260,000

= 9,040,000J

1,389.

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

α = L2L1L1×Δθ

18 x 10-6 = L222×100

L = 2.0036m

1,390.

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

θoC ... 60oS

0oC ... 30oS

θ01000 = 60(30)90(30)

θ = 75oC