JAMB Physics Past Questions & Answers - Page 35

171.
172.

Heat is supplied uniformly at the rate of 100W to 1.0 x 10\(^{-2}\)kg of a liquid for 20 seconds. If the temperature of the liquid rises by 5\(^o\)C, then the specific heat capacity of the liquid is 

A.

2.0 x 10\(^2\)Jkg\(^-1\)K\(^-1\)

B.

2.0 x 10\(^2\)Jkg\(^-1\)

C.

4.0 x 10\(^4\)Jkg\(^-1\)K\(^-1\)

D.

4.0 x 10\(^4\)Jkg\(^-1\)

Correct answer is C

Heat energy = Electrical Energy 

MC\(\theta\) = power x time 

5 x 1 x 10\(^{-2}\) x C = 100 x 20 

C = \(\frac{200}{5 \times 10^2}\) 

= 4 x 10\(^4\) J/kg/\(^oC\) 

173.

The lower and upper fixed points marked on a Mercury-in-glass thermometer are 210mm apart. The end of the mercury column in the tube is 49mm above the lower fixed point in a room. What is the temperature of the room in degrees Celsius? 

A.

55.3\(^o\)C

B.

23.3\(^o\)C

C.

49.0\(^o\)C

D.

16.43\(^o\)C

Correct answer is B

\(\frac{49 - 0}{210 - 0}\) = \(\frac{\theta - 0}{100 - \theta}\) 

\(\frac{49}{210} = \frac{\theta}{100}\) 

49 x 100 = 210 x \(\theta\) 

\(\theta = \frac{4900}{210}\) = 23.3\(^o\)

174.

The linear expansivity of brass is 2 x 10\(^{-5}\)  \(^oC^{-1}\). If the volume of piece of brass is 10cm\(^3\) at 0\(^o\)C. What will be its volume at 100\(^o\)C? 

A.

10.06cm\(^3\)

B.

10.04 cm\(^3\)

C.

10.02 cm\(^3\)

D.

10.20 cm\(^3\)

Correct answer is A

3 x \(\alpha\) = \(\frac{V_2 - V_1}{V_1 \times \Delta \theta}\)

3 x 2 x 10\(^{-5}\) = \(\frac{V_2 - 10}{100 \times 10}\) 

V\(_2\) = (100 x 10 x 3 x 2 10\(^{-2}\)) + 10

= 10.06 cm\(^3\)