JAMB Physics Past Questions & Answers - Page 364

1,816.

When the human eye loses its power of accomodation, the defect is known as

A.

short sightedness

B.

presbyopia

C.

astigmatism

D.

long sightedness

Correct answer is B

presbyopia is loss of accommodation

1,817.

Three similar cells each of e.m.f 2 v and internal resistance 2Ω are connected in parallel, the total e.m.f and total internal resistance are respectively

A.

6 v, 6.0Ω

B.

2 v, 0.7Ω

C.

2 v, 6.0Ω

D.

6 v, 0.7Ω

Correct answer is B

Total energy in parred connection is equal to emt of one cell, = 2v but total internal resistance is given by
(1)/r = (1)/r1 + (1)/r2 + (1)/r3 = (1)/2 + (1)/2 + (1)/2 = (3)/2
∴ r = (2)/3 = 0.67Ω

1,818.

I. change of state
II. Diffusion
III. Radiation
IV. Osmosis
which of the processes above can be explained using the kinetic theory?

A.

I, II,III and IV

B.

I, II and III

C.

I, III and IV

D.

I, II and IV

Correct answer is D

No explanation has been provided for this answer.

1,819.

Steam burn is more severe than that of boiling water because

A.

steam burn is independent of relative humidity

B.

steam possesses greater heat energy per unit mass

C.

water boils at a higher temperature

D.

steam burn is dependent on relative humidity

Correct answer is B

The specific latent heat of vaporization of steam is 2.1 x 106JKg-1
while the energy required to raise the temperature of a unit mass of water from 0°c to 100°c = C x Dt = 4200 x 100 = 420000 = 4.2 x 105 JKg-1
∴ steam possesses greater heat energy per unit mass

1,820.

A block of aluminum is heated electrically by a 30 w heater if the temperature rises by 10°c in 5 minutes, the heat capacity of the aluminum is

A.

900 JK-1

B.

90 JK-1

C.

100 JK-1

D.

200 JK-1

Correct answer is A

Heat supplied = Heat gained Pt = MCDθ
30 x 5 x 60 = c x 10
where c = mc which is the heat capacity
c = (30 x 5 x60)/10 = 900 JKg-1