1993 - WAEC Physics Past Questions and Answers - page 5
41
A particle of charge 5C moves perpendicularly to a magnetic Held of magnitude C.01 T. If the velocity of the charge is 1.5ms'2, calculate the magnitude of the force exerted on the particle
A
0.050 N
B
0.075N
C
0.0300N
D
3.300N
42
The function of the magnanese (IV) oxide in a leclanche cell is to
A
decrease the e.m.f. of the cell
B
prevent local action in the cell
C
prevent polarization in the cell
D
increase the density of the electrolyte
correct option: c
Users' Answers & Comments43
In the diagram above, three identical lamps each of 100 W are connected in parallel across a potential difference of 250 V. Calculate the reading of the ammeter.
A
7.5A
B
2.5A
C
1.2A
D
0.8A
correct option: c
P = VI ; I = P/V = 100/250 = 0.4A each
Total current 3 x 0.4 = 1.2A
Users' Answers & CommentsTotal current 3 x 0.4 = 1.2A
44
Electrical resistance is the property of an electrical conductor that causes electrical energy to be converted into
A
mechanical energy
B
solar energy
C
heat energy
D
magnetic energy
correct option: c
Users' Answers & Comments45
Calculate the current, I in the diagram shown above.
(Neglect the internal resistance of the cell)
(Neglect the internal resistance of the cell)
A
4.0A
B
2.0A
C
1.0A
D
O.5A
correct option: c
R = 2 + 2 = 4 Ω; 1/R = ¼ + ¼ = 2/4; R = 2Ω
∴ I = V/R = 2/2 = 1A
Users' Answers & Comments∴ I = V/R = 2/2 = 1A
46
Which of the following is not a conductor of electricity?
A
Human body
B
Glass
C
Silver
D
Earth
correct option: b
Users' Answers & Comments47
ln the diagram below, the galvanometer indicates a null-deflection. What is the potential difference between P and Q?
A
0.0 V
B
1.5 V
C
2.0 V
D
3.0V
correct option: a
Users' Answers & Comments48
When a potential difference, V is applied across the ends of a resistor of resistance, R a Current, l passes through the resistor. The heat generated in the resistor in time, t is given by the expression
A
V2lt
B
I2t/R
C
l2Rt
D
lR2tR
correct option: c
Users' Answers & Comments49
Electric motor primarily converts
A
electrical energy into chemical energy
B
electrical energy into heat energy
C
kinetic energy into potential energy
D
electrical energy into mechanical energy
correct option: d
Users' Answers & Comments50
What amount of current would pass through a 10 Ω coil if it takes 21s for the coil to just melt a lump of ice of mass 10g at 0oC if there are no heat losses? (Latent heat of fusion of ice = 336 Jg\(^{-1}\)).
A
16.00A
B
4.00 A
C
0.50A
D
0.25A
correct option: b
I\(^2\)Rt = mI;
I = \(\sqrt{\frac{mI}{Rt}}\)
= \(\sqrt{\frac{10 \times 336}{10 \times 21}}\)
= \(\sqrt{16}\)
= 4.0A