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JAMB Physics Past Questions & Answers - Page 200

996.

Which of the following is NOT directly associated with direct current (DC)?

A dry cell

a moving coil galvanometer

a transformer

a lead- acid accumulator

a commutator

View answer & explanation

Correct answer is C

No explanation has been provided for this answer.

997.

The extension in a spring when 5g wt was hung from it was 0.56cm. If Hooke's law is obeyed, What is the extension caused by a load of 20g wt?

1.12m

2.14cm

2.52cm

2.80cm

2.24cm

View answer & explanation

Correct answer is E

Extension & Load

Extension = K constant

$\frac{\text{load}}{0.56cm}$ = $\frac{X}{20g}$

X = 2.24cm

998.

A liquid-in-glass thermometer should quickly register temperature changes. This is achieved by choosing a liquid that

is opaque

has high density

has regular expansion

has a high thermal conductivity

can wet glass

View answer & explanation

Correct answer is D

No explanation has been provided for this answer.

999.

An object placed on the principle axis of a convex lens of focal length 10m produces a real image of double magnification. The image distance from the lens is

30cm

25cm

20cm

15cm

10cm

View answer & explanation

Correct answer is A

$\frac{1}{v}$ + $\frac{1}{u}$ = $\frac{1}{f}$

$\frac{1}{v}$ = +ve real image distance

where; U = +ve real object distance

f = real focus = 10

m = magnification

M = 2 = $\frac{v}{u}$

2u = V

$\frac{1}{2u}$ + $\frac{1}{u}$ = $\frac{1}{10}$

2u = 30

u = 15cm

v = 2u = 2 x 15

= 30cm