JAMB Physics Past Questions & Answers - Page 199

991.

If the volume of a fixed mass of a gas is kept constant, the pressure of the gas

A.

is inversely proprotional to its centigrade temperature

B.

is inversely proportional to its absolute temperature

C.

is directly proportional to its centigrade temperature

D.

is directly proportional to its absolute temperature

E.

remains constant also

Correct answer is D

Gay-Lussac's Law states that the pressure of a given mass of gas varies directly with the absolute temperature of the gas, when the volume is kept constant.

992.

Heat is supplied to a block of ice 0o until half of it has melted. Which of the following statements is true?

A.

the temperature rises and the ice expands

B.

the temperature remains constant and the volume of ice decreases

C.

the ice gives out heat as it melts

D.

the mass remains constant and the temperature increases

E.

the mass decreases because some heat is lost to the atmosphere

Correct answer is B

No explanation has been provided for this answer.

993.

The relative densities of zinc, brass, copper, gold and silver are respectively 7.1, 8.5, 8.9, 19.3, 10.5. A metal ornament which weighs 0.425kg and can displace 50 x 10-6m3 of water is made of

A.

zinc

B.

brass

C.

copper

D.

gold

E.

silver

Correct answer is B

R.D = \(\frac{\text {density of object}}{\text{density of water}}\)

= \(\frac{\frac{0.425}{50 10^-6}{1000}\)

= 8.5

994.

An object of mass m and volume v, is totally immersed in a liquid of density p. The tension of a string holding it is

A.

mg

B.

(m + pv)g

C.

(m - pv)g

D.

pvg

E.

[M/m-pv]g

Correct answer is C

Tension = upthrust on object

= weight in air - weight i liga

= mg - pvg

= (m - pv)g

995.

A milliameter of resistance 5\(\Omega\) and full scale deflection of 5m A is to used to measure a potential difference of 50 V. The resistance of the multiplier should be

A.

95\(\Omega\)

B.

110\(\Omega\)

C.

595\(\Omega\)

D.

995\(\Omega\)

E.

1005\(\Omega\)

Correct answer is D

V = IR

50 = 50 x 10-3 (5 + R)

R = 995\(\Omega\)