JAMB Physics Past Questions & Answers - Page 253

1,261.
1,262.

The vacuum in a thermos flask helps to reduce heat transfer by?

A.

convection and radiation

B.

convection and conduction

C.

conduction and radiation

D.

radiation only

Correct answer is B

No explanation has been provided for this answer.

1,263.

In which of the following are the substance arranged in descending order of their thermal conductivities?

A.

copper, steel, glass

B.

steel, copper, glass

C.

steel, glass, copper

D.

copper, glass, steel

Correct answer is A

No explanation has been provided for this answer.

1,264.

22,000J of heat is required to raise the temperature of 1.5kg of paraffin from 20oC to 30oC. Calculate the specific heat capacity of paraffin.

A.

1466Jkg-1 oC-1

B.

2933Jkg-1 oC-1

C.

4400Jkg-1 oC-1

D.

5866Jkg-1 oC-1

Correct answer is A

22,000 = 1.5 x c x (30 - 20)

c = 1466Jkg-1 oC-1

1,265.

Hot water is added to three times its mass of water at 10oC and the resultant temperature is 20oC. What is the initial temperature of the hot water?

A.

100oC

B.

80oC

C.

50oC

D.

40oC

Correct answer is C

Heat loss = heat gained

mh x ch x \(\theta\)h = mc x cc x \(\theta\)c

mh x ch x (\(\theta\) - 20) = mc x cc x (20 - 10)

ch = cc ; mc = 3mh

therefore, \(\theta\) = 50oC