JAMB Physics Past Questions & Answers - Page 293

1,461.

At constant pressure, the density of a fixed mass of gas is

A.

constant with temperature

B.

proportional to its volume

C.

inversely proportional to its temperature

D.

independent of its volume

Correct answer is C

Density = mass/ volume

At constant pressure, volume is directly proportional to Temperature

Density is inversely proportional to the volume at constant mass

At constant pressure, volume = constant x temperature

hence, density = mass/ (constant x temperature)

which shows density is inversely proportional to temperature

1,462.

One of the most important applications of bi-metallic strip is found in the construction of

A.

a thermostat

B.

an altimeter

C.

a thermocouple

D.

a hydrometer

Correct answer is A

No explanation has been provided for this answer.

1,463.

A bridge made of steel is 600m long. What is the daily variation in its length if the night-time and daytime temperatures are 10°C and 35°C respectively. The linear expansivity of steel is 0.000012C\(^{-1}\).

A.

0.18cm

B.

1.80cm

C.

18.00cm

D.

1800cm

Correct answer is C

\(\alpha\) = \(\frac{extension}{L\Delta\theta}\)

0.000012 = \(\frac{e}{600 \times (35 - 10}\)

= 0.18m

= (0.18 x 100) cm

= 18.0 cm

1,464.

A platinum resistance thermometer wire has a resistance of 5 ohms at 0oC and 5.5 ohms at 100oC. Calculate the temperature of the wire when the resistance is 5.2 ohms

A.

80oC

B.

60oC

C.

40oC

D.

10oC

Correct answer is C

100oC .... 5.5

\(\theta\)oC .... 5.3

0oC .... 5.0

\(\frac{\theta - 0}{100 - 0}\) = \(\frac{5.5 - 5 .0}{5.5 - 5.0}\)

\(\theta\) = 40oC

1,465.

If a plastic sphere floats in water (density = 1000kgm3) with 0.5 of its volume submerged, and floats in oil with 0.4 of its volume submerged the density of the oil is

A.

800kgm3

B.

1200kgm3

C.

1250kgm3

D.

2000kgm3

Correct answer is A

R.d = \(\frac{0.4}{0.5}\) = 0.8

0.8 = \(\frac{\text {Density of oil}}{\text{Density of water}}\)

0.8 = \(\frac{\text {Density of oil}}{1000}\)

Density of oil = 800kgm3