2014 - WAEC Physics Past Questions and Answers - page 4
31
an observer hears an echo 1.26 seconds after blowing a whistle near a cliff. calculate the distance of the observer from the cliff. [speed of sound in air = 330ms-1]
A
104.4m
B
207.9m
C
415.8m
D
523.8m
32
An object is placed in front of two plane mirrors inclined at 60o to each other. Determine the number of the images formed
A
2
B
3
C
5
D
7
correct option: c
n = \(\frac{360}{\theta}\) - 1
= \(\frac{360}{60} -1\)
= 6 - 1 = 5
Users' Answers & Comments= \(\frac{360}{60} -1\)
= 6 - 1 = 5
33
An ammeter can be adapted to measure potential difference by using a
A
shunt
B
multiplier
C
rheostat
D
resistance box
correct option: b
Users' Answers & Comments34
The region around a magnet in which magnetic force can be expressed is known as
A
declination
B
flux density
C
field
D
flux
correct option: c
Users' Answers & Comments35
In an ac circuit when the supply voltage frequency is equal to the resonant frequency, the current
A
leads the supply voltge by 90o
B
lags behind the supply voltage by 90o
C
leads the supply voltage by 45o
D
is in phase with the supply voltage
correct option: d
Users' Answers & Comments36
The energy stored in a simple cell is
A
electrical
B
nuclear
C
thermal
D
chemical
correct option: d
Users' Answers & Comments37
Which of the following conditions occur at resonance in a series RLC circuit? i. Impedance equal resistance ii. Current is maximum iii. Reactance are maximum iv. Current and voltage are 90o out of phase
A
i and ii only
B
i and ii only
C
i, ii and iii only
D
i, ii, iii and iv
correct option: a
Users' Answers & Comments38
An electric motor converts
A
electrical energy to mechanical energy
B
mechanical energy to electrical energy
C
mechanical energy to chemical energy
D
electrical energy to thermal energy
correct option: a
Users' Answers & Comments39
A 15 \(\mu F\) capacitor is connected to a 240V, 50Hz ac. source. Calculate the reactance of the capacitance [\(\pi = 3.142\)]
A
16\(\Omega\)
B
68\(\Omega\)
C
106\(\Omega\)
D
212\(\Omega\)
correct option: d
\(X_c = \frac{1}{2 \pi fc}\)
= 2 x 3.142 x 50 x 15 x 10-6
= 212.179\(\Omega\)
Users' Answers & Comments= 2 x 3.142 x 50 x 15 x 10-6
= 212.179\(\Omega\)
40
Two identical charges situated 20cm apart in vacuum repel each other with a force of 1.0N.Calculate the value of each other with a force of 1.0N. Calculate the value of each charge. [(14 \(\pi \varepsilon_o)^{-1}\) = 9 x 109Nm2C-2]
A
21\(\mu C\)
B
3.6\(\mu C\)
C
4.0\(\mu C\)
D
4.4\(\mu C\)
correct option: a
F = \(\frac{Q^2}{4 \pi \varepsilon_o r^2}\)
I = 9 x 109 x \(\frac{Q^2}{0.2^2}\)
Q = \(\sqrt{\frac{0.04}{9 \times 10^9}}\)
= 2.11 x 10-6
Users' Answers & CommentsI = 9 x 109 x \(\frac{Q^2}{0.2^2}\)
Q = \(\sqrt{\frac{0.04}{9 \times 10^9}}\)
= 2.11 x 10-6