JAMB Physics Past Questions & Answers - Page 200

997.

A stand-by generator is connected to fifteen 40 W lamps and musician's 600 W amplifying system. How much energy is used if the generator runs for 6 hours?

A.

3.84k Wh

B.

7.20k Wh

C.

8.40k Wh

D.

12.00k Wh

E.

14.56k Wh

Correct answer is B

Total power = (15 x 40) + 600

= 1200 watts

Energy(kWh) = \(\frac{1200}{1000}\) x 6

= 7.2 kwH

998.

A quantity of sungas at -133 occupies 1/3m3 under pressure 1.4 x 105 Nm-2. if the gas occupies 31 m-2 at 37oC, its pressure will be

A.

1.26 x 103Nm-2

B.

3.3 x104Nm-2

C.

1.35 x 104Nm-2

D.

2.2 x 104Nm-2

E.

105Nm-2

Correct answer is B

\(\frac{P_1V_1}{T_1}\) = \(\frac{P_2V_2}{T_2}\)

= \(\frac{\frac{1}{3} \times 1.4 \times 10^5}{-133 + 273}\) = \(\frac{P_2\times31}{37 +273}\)

P2 = 3.3 x 10

999.

If the magnification of a virtual image formed of an object 10cm from a convex lens is 3, then the focal length of the lens is

A.

10cm

B.

15cm

C.

16cm

D.

19cm

E.

20cm

Correct answer is B

V = 3u, U = 10cm

therefore U = -ve,

F = \(\frac{UV}{U + V}\)

= \(\frac{10 \times (-30)}{10 - 30 }\)

= 15cm