1992 - JAMB Physics Past Questions & Answers - page 1

1
The angle between the direction of the earth's magnetic field and the horizontal is called the
A
angle of deviation
B
magnetic declination
C
magnetic meridian
D
angle of dip
CORRECT OPTION: d
2
Calculate the force acting on an electron of charge 1.6 x 10-19C placed in an electric field of intensity 108Vm-1
A
1.6 x 10-11N
B
1.6 x 10-14N
C
1.6 x 10-16N
D
1.0 x 10-16N
CORRECT OPTION: a
F = EQ

1.6 x 10-19 x 108

= 1.6 x 10-11N
3
When an ebolite rod is rubbed with fur, it has
A
no charge at all
B
a negative charge
C
a positive charge
D
negative and positive charges
CORRECT OPTION: b
4
Which of the following factors has no effect on the e.m.f. of a primary cell?
A
temperature
B
size of the cell
C
nature of the plate
D
nature of the electrolyte
CORRECT OPTION: b
5
A wire of length 15m made of a material of resistivity 1.8 x 10-6\(\Omega\)m has a resistance of 0.27\(\Omega\). Determine the area of the wire
A
1.5 x 10-4m2
B
1.0 x 10-4m2
C
2.7 x 10-5m2
D
7.3 x 10-6m2
CORRECT OPTION: b
Resistivity = \(\frac{\text {Resiatance x Area}}{length}\)

1.6 x 10-6 = \(\frac{15 \times Area}{0.27}\)

Area = 1.0 x 10-4m2
6
A 5-v battery is connected across the plates of a 2.0\(\mu\)F uncharged parallel plate capacitor. The charge on the capacitor after a long time is
A
2.5\(\mu\)C
B
10.0\(\mu\)C
C
20.0\(\mu\)C
D
50.0\(\mu\)C
CORRECT OPTION: b
Q = cv

= 2 x 10-6 x 5

= 10 x 10-6C

= 10.0\(\mu\)C
7
Which of the following apparatus will require the smallest fuse rating for its protection?
A
60W, 240V
B
60W, 40V
C
40W, 12V
D
40W, 5V
CORRECT OPTION: a
I = \(\frac{P}{V}\) = \(\frac{60}{240}\) = 0.25A

I = \(\frac{P}{V}\) = \(\frac{60}{40}\) = 1.5A

I = \(\frac{P}{V}\) = \(\frac{40}{12}\) = 3.3A

I = \(\frac{P}{V}\) = \(\frac{40}{5}\) = 8A
8
The heat produced in a conductor carrying an electric current is
A
inversely proportional to the current and the resistance
B
directly proportional to the current, resistance and the time
C
inversely proportional to of the resistance, current and the time
D
directly proportional to the square of the current, the resistance and the time
CORRECT OPTION: d
9
The maximum permissible current through a galvanometer G of internal resistance 10\(\Omega\) is 0.05A. A resistance R is used to convert G into a voltmeter with a maximum reading of 100V. Find the value of R and how it is connected to G
A
20,000 ohms in parallel
B
19,990 ohms in series
C
1990 ohms in series
D
100 ohms in series
CORRECT OPTION: c
10
In alternating current theory, the units of impedance, r.m.s. voltage and resonance frequency are respectively equal to
A
volt, ampere and hertz
B
ohms, volt and hertz
C
watt, ohms and radian
D
ohms, hertz and joule
CORRECT OPTION: b
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