1990 - WAEC Physics Past Questions and Answers - page 5
41
A work of 30 joules is done is transferring 5 millicoulombs of charge from a point B to a point A in an electric Held. The potential difference between B and A is
A
1.7 x 10-4V
B
3.4x10-4V
C
1.5x10-1V
D
6.0 x103V
42
What is the value of R when G shows no deflection in the circuit illustrated above?
A
80Ω
B
75Ω
C
45Ω
D
20Ω
43
A charge of 1.0 x 10-5 Coulombs experience force of 40N at a certain point in space. What is the electric field intensity?
A
8.00 x 106NC-1
B
4.00 x 106NC-1
C
4.00 x 10-4NC-1
D
2.00 x 10-4NC-1
44
If the frequency of the ac. circuit illustrated above is 500/Ï€ Hz what would be the reactance in the circuit?
A
0.0009Ω/π
B
100Ω
C
1030Ω
D
1400Ω
45
Calculate the resistance of the filament of a lamp rates 240 V, 40 W
A
240Ω
B
360Ω
C
720Ω
D
1440Ω
46
Birds can perch safely on overhead electric power cables without being electrocuted because
A
birds can withstand high p.d. of the electric power cables
B
any accumulated charge on the birds is quickly dissipated
C
the feet of the birds are well insulated
D
the current is a.c. and has particular direction
47
A cell of e.m.f. 1.5 V and internal resistance of 2.59 is connected in series with an ammeter of resistance 0.59 and a resistor of resistance 7.09. Calculate the current in the circuit.
A
0.15 A
B
0.20 A
C
0.60A
D
3.00A
48
A rectangular coil of wire can rotate in a magnetic field. The ends of the coil are soldered to the two halves of a split ring. Two carbon brushes are made to press lightly against the split ring and when these are connected in circuit with a battery and rheostat, the coil rotates. This is a description of
A
a suspended- coil vanometer
B
a moving-cell ammeter
C
a d.c generator
D
an electric motor
49
How long will it take to heat 3 kg of water from 28oC to 88oC in an electric taking a current of 6 A from an e.m.f. source of 220V?
A
96s
B
1.20s
C
570s
D
600s
50
Which of the following reduce(s) the effect of the back e.m.f. generated in the primary coil of an induction coil? The capacitor in the circuit II. The make and break contact in the circuit III. The ratio of turns in the secondary to that in the primary
A
l only
B
II only
C
I and II only
D
II and III only
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