1992 - WAEC Physics Past Questions and Answers - page 5
41
Calculate the rate at which energy is used up in the circuit illustrated by the diagram
A
0 W
B
2 W
C
4 W
D
8 W
42
Which of the following is not a consequence of hydrogen bubbles covering the copper plate of a primary cell?
A
Polarization
B
Local action
C
Formation of hydrogen electrode
D
Increase in the resistance of the cell
43
Calculate the length of a constantan wire of cross- sectional area 4 π x 10-8m2 and resistivity 1.1 x 10-6 Ω m required to construct a standard resistor of resistance 21 Ω. [Take π = 22/7]
A
0.42m
B
2.40 m
C
6.25 m
D
183.75 m
44
In a domestic circuit, electrical appliances and lamps are arranged in parallel across the mains so as to enable the
A
same current to flow through the electrical appliances and the lamps
B
maximum energy to be consumed at least cost
C
same fuse to be used for the electrical appliances and the lamps
D
voltage across the appliances not to be affected when the lamps are switched on and off
45
Calculate the time in which 4.8 kJ of energy would be expended when an electric heater of resistance 1.8 x 103Ω is used on a 240 V mains supply. (Neglect heat losses to the surrounding).
A
150.0s
B
90.0s
C
36.0s
D
20.0s
46
Lenz’s law of electromagnetic induction states that
A
electromotive force is induced in a circuit whenever there is a change in the magnetic flux linked with the circuit
B
the induced current in a conductor is in such a direction as to oppose the change producing it
C
the induced e.m.f. in a circuit is proportional to the rate of change of number of lines of force linking the circuit
D
a force is exerted on a current carrying conductor in a magnetic field
47
Which of the following statements is not correct?
A
A magnetic Held is a region where a magnetic force can be detected.
B
Magnetic fields are scalar quantities.
C
The magnitude of the magnetic force experienced by a moving charge depends on the speed on the charge.
D
the angle between the direction of the earth’s magnetic held and the horizontal is called the angle of dip.
48
Calculate the energy stored in 20μF capacitor if the potential difference between the plates is 40 V.
A
3.2 x10-2J
B
1.6x102J
C
8.0x10-4J
D
4.0x10-4J
49
The diagrams above show lines of force in electric fields. In which of the diagrams would a positive test charge experience the least force as it moves from x to y?
A
I only
B
II only
C
III only
D
I and II only
50
What is the electric potential at a point distance r from a proton of charge q placed in a medium of permittivity εo?
A
q2/4πεor2
B
q/4πεor2
C
q2/4πεor
D
qr/4πεo
Loading lesson…