An electric lamp is rated 240V, 40W. What is the cost of running the lamp for 72 hours if the electricity authority charges N2.50 per kWh?
AN7.20
BN18.00
C180.00
DN720.00
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Question 32
waec2005
a chemical cell of internal resistance 1\(\Omega\) supplies electric current to an external resistor of resistance 3\(\Omega\). Calculate the efficiency of the cell
A75%
B50%
C33%
D25%
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Question 33
waec2005
A parallel plate capacitor of capacitance 600\(\mu F\) has a potential difference of 200V between its plates. Calculate the charge on either plate of the capacitor
A1.2C
B3.3C
C3330.0C
D12.0000.0C
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Question 34
waec2005
A parallel plate capacitor of capacitance 600\(\mu F\) has a potential difference of 200V between its plates. Calculate the charge on either plate of the capacitor
A1.2C
B3.3C
C3330.0C
D12.0000.0C
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Question 35
waec2005
Two capacitors if capacitance 0.4\(\mu F\) and 0.5\(\mu F\) are connected in parallel and charged to a p.d. of 50V, Determine the total charge acquired
A45\(\mu C\)
B25\(\mu C\)
C20\(\mu C\)
D10\(\mu C\)
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Question 36
waec2005
The ability of a material to store an electric charge when its plates are at different potentials is referred to as its
Aconductance
Binductance
Ccapacitance
Dresistance
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Question 37
waec2005
In which of the following media is the transmission of sound wave fastest?
AVacuum
BAir
CWood
DIron
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Question 38
waec2005
A ray of light is incident normally on a plan mirror. If the incident ray is kept fixed while the mirror is rotated through an angle of 30o, determine the initial and final angles of reflection respectively
A0o and 60o
B90o and 30o
C0o and 30o
D90o and 60o
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Question 39
waec2005
Which of the following optical instruments does not depend on the use of plane mirrors?
Akaleidoscope
Bsimple microscope
Csextant
Dsimple periscope
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Question 40
waec2005
The amplitude of a wave is the
Adistance travelled by the wave in a complete cycle of its motion
Bmaximum diplacement of the wave particle from the equilibrum position
Cseparation of two adjacent particles vibrating in a phase
Ddistance between two successive troughs of the wave
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Question 41
waec2005
Radio waves travel in air at 3.0 x 108ms-1. If the waves enter water of refractive index \(\frac{4}{3}\), calculate the speed of radio waves in water
A4.33 x 108ms-1
B4.00 x 108ms-1
C2.25 x 108ms-1
D1.33 x 108ms-1
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Question 42
waec2005
The distance between two points in phase on a progressive wave is 5cm. If the sped of the wave is 0.2ms-1, calculate its period
A4.00s
B2.50s
C0.25s
D0.04s
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Question 43
waec2005
Which of the following statements about a progressive mechanical wave is correct?
Ait can be a plane polarised
Bits energy is localised at specific points of its profile
Cit does not require a material medium for its propagation
Dits frequency remains constant as it travels between different media
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Question 44
waec2005
The pressure exerted by a given mass of gas in a container
Adecreases if the container is heated
Bincreases if the molecules of the gas move faster
Cincreases if the container is doubled
Ddecreases as the kinetic energy of the gas molecules inceases
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Question 45
waec2005
Which of the following statements is correct?
Athe density of a liquid decreases when it expands
Bthe density of a liquid increases when the liquids are heated
Cthe real expansivity of a liquid is less than its apparent expansivity
Da liquid changes to solid when heated to a sufficiently high temperature
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Question 46
waec2005
Which of the following statements about boiling and evaporation at atmospheric pressure is correct?
Aevaporation and boiling of water take place at 100o
Bevaporation of water takes place at a temperature greater than 100oC, while boiling takes place at 100oC
Cevaporation of water takes place at 100oC while boiling takes place at a higher temperature
Dboiling takes place at 100o while evaporation my take place at temperatures lower than 100oC
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Question 47
waec2005
The energy required to change a solid to liquid at constant temperature is called
Athermal capacity
Bhas lower specific heat capacity
Clatent heat of fusion
Dlatent heat of vaporisation
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Question 48
waec2005
Water falls through a height of 50m. Determine the temperature rise at the bottom of the fall. [Neglect energy losses. Specific heat capacity of water = 4200Jkg-1 K-1, g = 10ms2]
A0.119oC
B0.840oC
C1.190oC
D8.400oC
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Question 49
waec2005
An immersion heater rated 400W, 220V is used to heat a liquid of mass 0.5kg. If the temperature of the liquid increases uniformly at the rate of 2.5oC per second, calculate the specific heat capacity of the liquid. [Assume no heat is lost]
A1100Jkg-1K-1
B320Jkg-1K-1
C200Jkg-1K-1
D176Jkg-1K-1
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Question 50
waec2005
A body of mass m, has a specific heat capacity s, and a heat capacity c. If the temperature of the body changes by \(\theta^oC\), Which of the following equation is correct?
