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JAMB Physics Past Questions & Answers - Page 34

166.

In the figure, the value of R is 

A.

3Ω

B.

6Ω

C.

4Ω

D.

5Ω

Correct answer is B

RT = V1=122 = 6Ω 

RT = 3 + R×6R+6 

R = 6Ω 

167.

In an experiment in which molten naphthalene is allowed to cool, the cooling curve i n the figure was obtained. The temperature 80oC is known as the 

A.

cooling temperature

B.

boiling point

C.

melting point

D.

vaporization point

Correct answer is C

No explanation has been provided for this answer.

168.

The fiqure above represents a block-and-tackle pulley system on which an effort of W Newtons supports a load of 120.0N. If the efficiency of the machine is 40o, then the value of W is 

A.

28.0N

B.

48.0N

C.

288.0N

D.

50.0N

Correct answer is D

V.E = 6, load = 120N 

Efficiency = M.A x 1V.R x 100%

40 = 120effort x 16 x 1001 

Effort = 50N

169.

Two divers G and H are at depths 20m and 40m, respectively below the water surface in a lake. The pressure on G is p1 while the pressure on H is P2, If the atmospheric pressure is equivalent to 10m of water, then the value of P2/P1 is?

 

A.

0.50

B.

0.60

C.

1.67

D.

2.00

Correct answer is C

Atmospheric pressure equivalence of 10m of water
: p2+10p1+10

= \frac{40+10}{20+10

 = 5030 = 1.67

170.

Heat is supplied uniformly at the rate of 100W to 1.0 x 102kg of a liquid for 20 seconds. If the temperature of the liquid rises by 5oC, then the specific heat capacity of the liquid is 

A.

2.0 x 102Jkg1K1

B.

2.0 x 102Jkg1

C.

4.0 x 104Jkg1K1

D.

4.0 x 104Jkg1

Correct answer is C

Heat energy = Electrical Energy 

MCθ = power x time 

5 x 1 x 102 x C = 100 x 20 

C = 2005×102 

= 4 x 104 J/kg/oC