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
correct option: b
Users' Answers & Comments43
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
correct option: d
Users' Answers & Comments45
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
correct option: b
Users' Answers & Comments47
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.
correct option: b
Users' Answers & Comments48
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
correct option: a
Users' Answers & Comments50
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
correct option: b
Users' Answers & Comments