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JAMB Physics Past Questions & Answers - Page 186

926.

A capacitor and a resistor are connected in series with each other and in series with an accumulator of negligible internal resistance. The potential across the terminals of the capacitor is

A.

twice the e.m.f of the accumulator

B.

less than the e.m.f by the potential drop across the resistor

C.

zero

D.

the same as the e.m.f.

E.

greater than

Correct answer is E

In D.C circuit,

Xc = infinity

therefore, Vc = infinity

927.

Consider a thick glass tumbler and a thin glass tumbler which are made of the same kind of glass. Some hot liquid is poured into them. Which of the following statements is correct?

A.

the thick tumbler is less likely to crack because it is stronger

B.

the thick tumbler is less likely to crack because it insulates the heat better, glass being a poor conductor of heat

C.

Both tumblers are equally likely to crack because they are made of the same kind of glass

D.

the thick tumbler is more likely to crack because uneven expansion persists for a longer time within the thicker glass

E.

the thick tumbler is more likely to crack because it is heavier

Correct answer is D

Usually,  when pour water into a glass, the more thick glass is easier to break. Because the glass tumbler is cold, when hot water is poured, and the inner wall expands rapidly due to thermal expansion and contraction.

929.
930.

The bulb of a motorcycle head-lamp is marked 40W, 6V. The resistance of the filament when it is switched on is

A.

62402ohms

B.

4062ohms

C.

406ohms

D.

6 x 40 ohms

E.

6240ohms

Correct answer is E

Power V2R

40 = 6×6r

R = 3640Ω