Calculate the time taken to heat 2kg of water from 50°C to 100°C in an electric kettle taking 5A, from a 210V supply. (Specific heat capacity of water = 4200\(kg^{-1}K{-1}\)
A2.5 minutes
B5.7 minutes
C6.7 minutes
D7.5 minutes
E9.5 minutes
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Question 772
waec1994
The pressure of air in a tire is \(22.5Nm^{-2}\) at 27°C. If the air in the tyre heats up to 47°C, calculate the new pressure of the air, assuming that no air leaks out and that the change in volume of the air can be neglected.
A\(21.10Nm^{-2}\)
B\(24Nm^{-2}\)
C\(39.07Nm^{-2}\)
D\(45Nm^{-2}\)
E\(97.25Nm^{-2}\)
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Question 773
waec1994
\(500cm^{-3}\) of a gas is collected at 0°C and at a pressure of 72cm of mercury. What is the volume of the the gas at the same temperature and at a pressure of 76cm of the same mercury?
A\(\frac{76\times500}{72}cm^3\)
B\(\frac{72\times500}{76}cm^3\)
C\(\frac{72\times76}{500}cm^3\)
D\(\frac{76}{72\times500}cm^3\)
E\(\frac{72}{76\times500}cm^3\)
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Question 774
waec1994
An electric kettle rated 1500W boils away 0.3kg of a liquid at its boiling point every 300s. Calculate the specific latent heat of the vaporisation of the liquid
A1.5 x \(10^6Jkg^-1\)
B1.35 x \(10^6Jkg^-1\)
C1.5 x \(10^5Jkg^-1\)
D4.5 x \(10^2Jkg^-1\)
E3 x \(10^2Jkg^-1\)
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Question 775
waec1994
500g of water is heated so that its temperature rises from 30°C to 72°C in 7 minutes. calculate the supplied per minute. (Specific heat capacity of water is 4200J\(kg^{-1}K^{-1}\)
A9000J
B12600J
C21000J
D25200J
E88200J
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Question 776
waec1994
A metal rod of length 40cm at 20°C is heated to a temperature of 45°C. If the new length of the rod is 40.05cm. Calculate its linear expansitivity
A1.2 x \(10^{-5}K{-1}\)
B2.5x \(10^{-5}K{-1}\)
C3.5x \(10^{-5}K{-1}\)
D4.5x \(10^{-5}K{-1}\)
E5x \(10^{-5}K{-1}\)
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Question 777
waec1994
A body accelerates uniformly from rest at \(2ms^{-2}\). Calculate the velocity after traveling 9m
A36\(ms^{-1}\)
B18\(ms^{-1}\)
C6\(ms^{-1}\)
D4.5\(ms^{-1}\)
E4.24\(ms^{-1}\)
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Question 778
waec1994
A ball is dropped from a height of 45m above the ground. Calculate the velocity of the ball just before it strikes the ground. (Neglect air resistance and take g as \(10ms^{-2}\)
A21.2\(ms^{-1}\)
B30\(ms^{-1}\)
C300\(ms^{-1}\)
D450\(ms^{-1}\)
E900\(ms^{-1}\)
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Question 779
waec1994
A cell of e.m.f. 1.5V and internal resistance of 2.5Ω is connected in series with an ammeter of resistance 0.5W and a resistor of resistance of 7.0Ω. Calculate the current in the circuit.
A0.15A
B0.20A
C2.10A
D3A
E6.6A
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Question 780
waec1994
A note of frequency of 2000Hz has a velocity of \(400ms^{-1}\). What is the wavelength of the note?
A800m
B200m
C5m
D2m
E0.2m
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Question 781
waec1994
The wave function of a metal is 8.0 x \(10^{-19}\)J. Calculate the wavelength of its threshold frequency. (Speed of light in a vacuum = 3 x \(10^8ms^{-1}, Planck's constant = 6.6 \times 10^{-34}\)Js)
A0.8 x \(10^{-7}\)m
B1 x \(10^{-7}\)m
C2.3 x \(10^{-7}\)m
D3.8 x \(10^{-7}\)m
E12.4 x \(10^{-7}\)m
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Question 782
waec1994
The nucleon number and the proton number of a neutral atom of an element are 238 and 92 respectively. What is the number of neutrons in the atom?
A330
B238
C146
D119
E73
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Question 783
waec1994
In 24 days a radioactive isotope decreases in mass from 64g to 2g. What is the half life of the radioactive material
A0.75 days
B2.58 days
C4 days
D4.80 days
E6 days
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Question 784
waec1994
When an atom loses or gains a charge, it becomes an
Aion
Ban electron
Ca neutron
Da proton
Ea deuteron
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Question 785
waec1994
Which of the following substances is not an insulator?
AAluminium
BGlass
CPlastic
DClay
ECork
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Question 786
waec1994
Beta particles are
Aelectrons
Bprotons
Cneutrons
Dhelium nuclei
Etritium nuclei
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Question 787
waec1994
A transformer with 5500 turns in its primary winding is used between a 240V a.c supply and 120V kettle. Calculate the number of turns in the secondary winding
A11000
B2750
C460
D550
E232
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Question 788
waec1994
Which of the following is a stringed instrument?
AFlute
BTrumpet
CPiano
DDrum
EOrgan
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Question 789
waec1994
A lamp marked 100W, 250V is lit for 10 hours. If it operates normally and 1KWh of electrical energy costs 2k, what is the cost of lighting the lamp?
A1k
B2k
C5k
D10k
E20k
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Question 790
waec1994
A particle of charge q and mass m moving with a velocity v enters a uniform magnetic field of strength B in the direction of the field. The force on the particle is
