2006 - WAEC Physics Past Questions and Answers - page 3
21
The silvered surface in a vacuum flask reduces heat loos due to
A
conduction
B
convection
C
radiation
D
evaporation
correct option: c
Users' Answers & Comments22
How long will it take to heat 3kg of water from 28oC to 88oC in an electric kettle taking 6a from a 220V supply? [specific heat capacity of water = 4180 J kg-1K-1]
A
120s
B
570s
C
600s
D
836s
correct option: b
t = \(\frac{mc\theta}{IV} = \frac{3 \times 4189 \times 60}{6 \times 120} = 570s\)
Users' Answers & Comments23
The amount of energy required to change a kilogram of ice in water without a change in temperature is
A
heat capacity of ice
B
specific heat capacity
C
specific latent heat of vaporisation of ice
D
specific latent heat of fusion of ice
correct option: d
Users' Answers & Comments24
A quantity of steam at 100oC condenses to water at the same temperature by releasing 6.9 x 104J of energy. Calculate the mass of the condensed steam. [specific latent heat of vaporization of eater = 2.3 x 106 J kg-1]
A
3.0 x 10-1 kg
B
3.0 x 10-2 kg
C
3.0 x 10-3 kg
D
3.0 x 10-4 kg
correct option: b
M = \(\frac{Q}{T} = \frac{6.9 \times 10^{4}}{2.3 \times 10^6} = 3 \times 10^{-2} kg\)
Users' Answers & Comments25
The temperature of a liquid falls after some of it has evaporated because
A
the liquid left is smaller in volume and the breeae easily cools it
B
the more energetic molecules have escaped into the atmosphere
C
the liquid left has less latent heat
D
after evaporation impurites are left behind
correct option: b
Users' Answers & Comments26
The S.I units of frequency, period and amplitude of a wave are respectively
A
hertz, second and centimeter
B
second, metre and hertz
C
metre, hertz and seconds
D
hertz, second and metre
correct option: d
Users' Answers & Comments27
a note of frequency 2000Hz has a velocity of 400 ms-1. calculate the wavelength of the note
A
5.0m
B
2.0m
C
0.5m
D
0.2m
28
The eclipse of the moon occurs when the
A
moon comes exactly between the earth and the sun
B
earth comes exactly between the moon and the sun
C
sun comes exactly between the earth and the moon
D
moon reflects all the rays from the sun onto the earth
correct option: b
Users' Answers & Comments29
Which of the following observations cannot be explained using the rectilinear propagation of light?
A
production of images by a pinhole camera
B
production of real images of objects by lenses
C
formation of an annular eclipse
D
diffraction patterns of light
correct option: d
Users' Answers & Comments30
The distance between the successive crests of a wave travelling at 20ms-1 is 25cm. Calculate the frequency of the wave
A
0.8Hz
B
5.0Hz
C
50.0Hz
D
80.0hz