1989 - WAEC Physics Past Questions and Answers - page 2
11
A thermometer has its stem marked in millimeter instead of degree Celsius. The lower fixed point is 30mm and the upper is 180mm. Calculate the temperature in degree celsius when the thermometer reads 45mm.
A
67.5oC
B
30.0oC
C
25.0oC
D
15.0oC
correct option: e
θ = (x/y) x 100.
where x = UFP -LFP -another scale, and y = UFP - LFP for celsius scale.
=> {(45-30)/(180-30)} x 100 = 10.0oC
Users' Answers & Commentswhere x = UFP -LFP -another scale, and y = UFP - LFP for celsius scale.
=> {(45-30)/(180-30)} x 100 = 10.0oC
12
Which of the following surfaces will radiate heat energy best?
A
Red
B
White
C
Black
D
Yellow
correct option: c
Users' Answers & Comments13
Which of the followiempeng statements is/are not correct?
A
Evaporation takes place only at the surface of the liquid
B
Boiling takes place throughout the volume of the liquid
C
Evaportaion takes place at all temperatures
D
Boiling takes place at a particular temperature for a liquid at a fixed external pressure
correct option: e
Users' Answers & Comments14
Water in an open container boils at a lower temperature when heated at the top of a mountain than at sea-level because at the top of a mountain the
A
relative humidity is higher than at sea-level
B
rays of the sun adds more heat to the water
C
temperature is lower than that at sea-level
D
pressure is lower than that at sea-level
correct option: d
Refer to Elementary physics, pressure reduces with height.
Users' Answers & Comments15
Which of the following substance is not a good conductor of electricity?
A
Human body
B
Glass
C
Aluminium
D
Earth
correct option: b
Users' Answers & Comments16
Calculate the heat energy required to vapourize 50g of water initially at 80oC if the specific heat capacity of water is 4.2Jg-1K (specific latent heat of vapourization of water is 2260Jg-1).
A
533000J
B
230000J
C
117200J
D
113000J
correct option: c
Q = McΔθ + ml
Q = {50 x 4.2 x (100 - 80) + 50 x 2260} 117200J.
Users' Answers & CommentsQ = {50 x 4.2 x (100 - 80) + 50 x 2260} 117200J.
17
A block of ice at its melting point is left on a table in the atmosphere and observed to melt gradually. Which of the following statements is true about the melting process?
A
the reaction force of the table on the ice breaks the ice into water molecules
B
heat extracted from the ice block makes the ice block cold
C
the ice block absorbs heat from the atmosphere and its temperature rises
D
the atmosphere absorbs heat from the ice block and its temperature falls
correct option: c
Users' Answers & Comments18
All the heat generated by a current of 2A passing through a resistor of 6Ω for 2.5s is used to evaporate 5 g of a liquid at its boiling point. What is the specific latent heat of the liquid?
A
60 Jg-1
B
120 Jg-1
C
300 Jg-1
D
360 Jg-1
correct option: b
Electrical Energy = Heat Energy.
I2Rt = ml
22 x 6 25 = 5 x L.
L = 120 Jg-1.
Users' Answers & CommentsI2Rt = ml
22 x 6 25 = 5 x L.
L = 120 Jg-1.
19
Which of the following instruments can be used to compare the relative magnitudes of charges on two given bodies?
A
The electrophorous
B
Ebonite rod
C
Proof plane
D
Gold leaf electroscope
correct option: d
Users' Answers & Comments20
A short chain is usual attached to the back of a petrol tanker trailing behind it to ensure that the
A
petrol tanker is balanced on the wh eel
B
heat generated by friction in the engine can be conducted to the floor
C
charges generated by friction in the tanker can be conducted to the earth
D
the tanker moves slowly as the chain touches the floor
correct option: c
Users' Answers & Comments