The greatest difference in pressure exerted on a smooth horizontal surface by the surfaces of a regular block of wood of dimensions 3.0cm by 4.0cm by 5.0cm and density 0.75g/c.c. is:-
A.225 N/m2
B.300 N/m2
C.150 N/m2
D.375 N/m2
12.1 mark
The normal body temperature of a healthy human being is 36.9°C. In the absolute temperature scale, this temperature is equivalent to:
A.309.9K
B.309.9°K
C.309.9°C
D.309.9C
19.1 mark
The magnetic field pattern produced by arrangement of magnetic pole pieces shown in figure 2 suggests that the letter R stands for:-
A.N pole
B.S pole
C.Dipole
D.Neutral point
20.1 mark
Three common methods of magnetization are:-
A.Natural, Electrical and Chemical
B.Electrical, Magnetic and Induction
C.Stroking, Induction and Electrical
D.Stroking, Chemical and Natural
21.1 mark
A milliammeter can be converted to an ammeter by connecting its coil to a suitable resistor called a:-
A.Multiplier in series
B.Shunt in series
C.Multiplier in parallel
D.Shunt in parallel
22.1 mark
If the plastic cap of a ball pen is rubbed against hair it tends to attract small pieces of paper. This effect is observed because the cap has been charged by:-
A.removal of electrons
B.addition of electrons
C.induction
D.contact
23.1 mark
Electrostatic charges are measured in terms of:-
A.Amperes
B.Farads
C.Electrons
D.Coulombs
24.1 mark
The time taken to deposit 99mg of copper in a copper voltameter which carries a current of 3.0 A is equal to:-
A.10.0 seconds
B.100.0 seconds
C.100,000.0 seconds
D.10,000.0 seconds
25.1 mark
The metal which emits electrons by thermionic emission in the triode tube is called a:-
A.hot cathode
B.cold cathode
C.cathode ray emitter
D.filament
26.1 mark
Select the incorrect statement from the following:-
A.Elements with the same atomic number have the same chemical properties
B.Elements with the same atomic number and different atomic masses are called isotopes.
C.The atoms of a given element do not necessarily have the same mass.
D.The atomic number of an element is equal to the sum of its mass number and its number of neutrons.
27.1 mark
A Geiger Muller Tube sealed into a radioactive source and connected to a decade counter records a count of 3200 per second for the source at 11.00 a.m. on Tuesday the 29th of October 1996 and 40 per second at 2.00 p.m. on the next day. From this observation it can be deduced that the half life of the source is:-
A.9.0 hours
B.6.0 hours
C.3.0 hours
D.1.0 hour.
28.1 mark
A transformer having 1000 turns in the primary coil and 250 turns in the secondary coil is supplied with 240 volts d.c. from a battery. Which of the following is the output voltage in the secondary?
A.60 volts a.c.
B.60 volts d.c.
C.960 volts a.c.
D.0 volts.
29.1 mark
Which of the following is a statement of Lenz’s law of electromagnetic induction?
A.The magnitude of the induced e.m.f. is proportional to the rate of change of flux.
B.The direction of the induced e.m.f. is such as to oppose the motion producing it.
C.The ratio of number of turns of coil in the primary to those of the secondary equals the ratio of primary voltage to secondary voltage.
D.The induced e.m.f. is produced in a straight conductor when the conductor cuts the magnetic flux.
Section B
2.5 marks
(a)
Draw a simple pulley machine whose velocity ratio is 3.
2 mk
(b)
If the efficiency of this machine is 80%, what load can be raised by an effort of 200 N?
3 mk
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3.5 marks
Is it possible for a balloon of volume 2000m$^3$ filled with hydrogen of density 0.09 kg/m$^3$ to float in air, if the mass of its canvas is 100 kg, that of the pilot is 70 kg and if it carries an extra load of 1500 kg? Explain your answer.
(none)
Determine if the balloon can float in air by comparing the total upward buoyant force with the total downward force (weight of hydrogen, canvas, pilot, and load). Assume the density of air is approximately 1.225 kg/m$^3$.
5 mk
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4.5 marks
(a)
What is limiting friction?
1 mk
(b)
A loaded trailer weighing 25 tonnes is being towed at constant speed across a level roadway whose coefficient of dynamic friction is 0.25. Determine the frictional force in the trailer?
4 mk
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5.5 marks
Explain how you would show in the Laboratory that water is a bad conductor of heat.
(none)
Describe a laboratory experiment to demonstrate that water is a poor conductor of heat. This should include the apparatus used, the procedure, and expected observations.
5 mk
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6.5 marks
(a)
What is electromagnetic radiation?
1 mk
(b)
Why are refrigerators painted white?
2 mk
(c)
Name two domestic utensils or appliances which are painted black and explain why they are painted so?
2 mk
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7.5 marks
Classify the following as “real” or “virtual” images:-
(i)
The image formed in a convex mirror
1 mk
(ii)
The image formed in a plane mirror
1 mk
(iii)
The image formed in a concave mirror when the object is positioned between the focal point and the pole point.
1 mk
(iv)
The image formed in a concave mirror when the object is positioned outside the focal length.
1 mk
(v)
The image formed by a pin hole camera.
1 mk
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8.5 marks
(a)
Define e.m.f. and internal resistance of a cell.
2 mk
(b)
A battery of e.m.f. 12.0V and internal resistance of 0.5Ω is connected to a parallel combination of resistors valued 15Ω and 30Ω. What current passes through each resistor?
3 mk
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9.5 marks
(a)
State the factors which determine the resistance of a conductor.
2 mk
(b)
Find the length of nichrome wire of diameter 0.56 mm which will provide a resistance of 100 Ω given that its resistivity is $10^{-6} Ωm$.
3 mk
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10.4 marks
(a)
Write down two ways in which a.c. power produces similar effects as d.c. power.
2 mk
(b)
Write one process which can be performed by d.c. power but not a.c. power.
1 mk
(c)
Write down two main advantages of usage of a.c. power over d.c. power for domestic and industrial purposes.
1 mk
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11.5 marks
(a)
Draw a fully labelled standard symbol of a p-n-p transistor.
3 mk
(b)
What is the main function of a transistor in an electronic circuit?
1 mk
(c)
Name one of the two common semiconductor materials used in solid state electronics.
1 mk
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13.8 marks
An eight tonne loaded truck travelling at 45 km/hr collides and sticks to two connected empty trucks each of mass 3.5 tonnes.
(i)
Find the initial speed of the three trucks if frictional effects are negligible.
3 mk
(ii)
How much energy is lost at impact?
3 mk
(iii)
How can you account for this lost energy?
1 mk
(iv)
Does this particular example support the conservation laws of momentum and energy?
1 mk
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14.10 marks
(a)
Write the names of each of the three states of water.
3 mk
(b)
Determine the amount of heat required to vapourize completely 100 grammes of ice initially at -10°C, given that the specific heat capacity of water is 4200J/kgK and the latent heat of vapourisation of water is 2,268,000 J/kg.
7 mk
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15.8 marks
(a)
Define focal point and pole point of a converging lens.
2 mk
(b)
Draw ray diagrams showing how a converging lens produces:
4 mk
(c)
An object is placed 20cm form a converging lens of focal length 8.0cm. By a drawing or otherwise find the distance of the image from the lens. What is the magnification?
4 mk
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16.10 marks
A Laboratory technician has enough stock of standard resistors of values 100Ω and 1000Ω. For each of the five resistors prepared by the technician in (a) above find the current that will pass through the effective resistor if a 6.0 volts battery of negligible internal resistance is connected across its ends.
(a)
Illustrate how he can prepare standard resistors of values 50Ω, 150Ω, 250Ω, 300Ω and 500Ω using combinations of not more than four resistors.
5 mk
(b)
For each of the five resistors prepared by the technician in (a) above find the current that will pass through the effective resistor if a 6.0 volts battery of negligible internal resistance is connected across its ends.
5 mk
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17.10 marks
Uranium 238U decays to Polonium 222P by α emission (at each stage) via 234Th, 230Ra and 226Rn. Following this process, 222P decays to qRn by β emission only. Write balanced equations of the stage by stage decay process from 238U to qRn and hence determine the values of x, y, z and q.
(a)
Define the terms isotopes and isobars.
2 mk
(b)
Uranium 238U decays to Polonium 222P by α emission (at each stage) via 234Th, 230Ra and 226Rn. Following this process, 222P decays to qRn by β emission only. Write balanced equations of the stage by stage decay process from 238U to qRn and hence determine the values of x, y, z and q.
6 mk
(c)
Name the isotopes and isobars obtained in the decay process shown in (b) above.
2 mk
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18.8 marks
(a)
Under what conditions are eddy currents formed?
2 mk
(b)
State two advantages and two disadvantages of eddy currents.
4 mk
(c)
What practical steps are taken in order to minimize eddy currents in the core of a transformer?
2 mk
(d)
Is it possible to construct a transformer with 100% efficiency? Why?
2 mk
