K.C.S.E Physics Q & A - MODEL 2005PP1QN35
Draw appropriate symbols the circuit diagram of a junction diode in reverse bias.
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K.C.S.E Physics Q & A - MODEL 2005PP1QN33
The target of X-ray tube s made of melting point. Give a reason for this
ANSWER
K.C.S.E Physics Q & A - MODEL 2005PP1QN29
A car of mass 800kg moves on a circular track of radius 20m. The force of friction between the tyres and the tarmac is 4800N Determine the maximum speed at which the car can be driven on the track without skidding.
K.C.S.E Physics Q & A - MODEL 2004PP2QN03
​ Figure 4 shows the cross-section of a diffusion cloud chamber used to detect radiation from radioactive sources.
a) i) State one function of each of the following:
Alcohol solid Co2 ii) When radiation from the source enters the chamber, some white traces are observed. Explain how these traces are formed and state how the radiation is identified. iii) A leaf electroscope can also be used as a detector of radiation. State two advantages of the diffusion cloud chamber over the leaf electroscope as a detector. b) i) Two samples of the same radioactive material have initial masses M and 2M respectively. On the axes provided, sketch the graph of activity versus time for each sample. Label the graph for each sample. ii) A radioactive sample of half-life 130 days initially has 1.0 x 102c radioactive atoms. Determine the number of radioactive atoms that have decayed after 390 days.K.C.S.E Physics Q & A - MODEL 2004PP1QN35&36
​Figure 18 shows the circuit of a npn-n transistor amplifier in common –emitter mode. Use the information on the figure to answer question 35 and 36
On the diagram
a) Label the collector current, Ic and IB b) Indicate the directions of 1c and 1B you have labeled in (a) above. Indicate on the diagram, the position where the output V0 would be tapped.
answer
K.C.S.E Physics Q & A - MODEL 2004PP1QN34The work function of a certain material is 3.2 3V. Determine the threshold frequency for the material. (1 electron Volt (eV)= 1.6 x10-19) and planks Constant h=6.62 x 10-34Js)K.C.S.E Physics Q & A - MODEL 2004PP1QN32
​Figure 17 shows the appearance of an alternating signal on a screen of a cathode ray oscilloscope.
On the same diagram, sketch the appearance of the signal when the frequency is doubled and the voltage halved.
K.C.S.E Physics Q & A - MODEL 2004PP1QN28
State the difference between X-rays and Gamma rays in the way in which they are produced.K.C.S.E Physics Q & A - MODEL 2004PP1QN21&22
​A certain powder of mass. 0.10kg was heated in a container by an electric heater rated 50 w for sometime. The graph below shows the variation of the temperature of the powder with time. Use this information and the graph to answer question
21 and 22.
i) Determine the quantity of heat by the heater from the time the power starts to melt to the time it has all melted.
ii) Determine the specific latent heat of fusion of powder assuming the container absorbs negligible amount of heat K.C.S.E Physics Q & A - MODEL 2004PP1QN20
​ An electric heater is connected to the mains supply. A fault in the mains reduces the supply potential slightly.
Explain the effect on the rate of heating of the heater. K.C.S.E Physics Q & A - MODEL 2003PP1QN34
​Figure 18 shows the pattern produced by an A.C voltage on a CRO screen.
​On the same figure, sketch the pattern produced by the same voltage when the time base is switched off.
K.C.S.E Physics Q & A - MODEL 2003PP1QN32&33
​Two identical copper coils p and Q are placed close to each other as shown in Figure 17. Coil P is connected to a D>C power supply and coil Q is connected to a galvanometer, G.
​Use this information to answer questions 32 and 33.
State and explain what would be observed on the galvanometer immediately the switch S is closed. State with reason the difference that would be noted in the observation made in question 32 if the number of turns in coils Q were doubled.
ANSWERS
K.C.S.E Physics Q & A - MODEL 2003PP1QN31
​ Arrange the following gin order of increasing frequency:
Visible light, infrared radiation, X – rays, u. v. radiation, radio waves.
ANSWER
K.C.S.E Physics Q & A - MODEL 2003PP1QN19
Pure silicon can be changed into p –type semiconductor by adding an impurity. Explain how this is achieved.
answer
K.C.S.E Physics Q & A - MODEL 2003PP1QN18
​ The following equation shows part of a radioactive decay process.
​Name the radiation x.
K.C.S.E Physics Q & A - MODEL 2002PP2QN07
​a) Fig. 8 shows ultra violet light striking a polished zinc plate placed on a negatively charged gold – leaf electroscope.
​Explain the following observations
i) The leaf of the electroscope falls. ii) When the same experiment was repeated with a positively charged electroscope the leaf did not fall. bi) State two factors which determine the speed of photoelectrons emitted by a metal surface ii) In an experiment using a photocell, u, v. light of varying frequency but constant intensity was made to strike a metal surface. The maximum kinetic energy (K.E max)of photoelectrons for each frequency, was measured. The graph shows how KE max varies with f
K.C.S.E Physics Q & A - MODEL 2002PP1QN32
State the property of X-rays, which makes it possible to detect cracks in bones.
answer
K.C.S.E Physics Q & A - MODEL 2002PP1QN31
A nucleus is represents by 10742x. State the number of neutrons in the nucleus.
answer
K.C.S.E Physics Q & A - MODEL 2002PP1QN30
The following table shows electrical appliances to be used in a house. The electrical rating for each appliance is shown. The following fuses are available, 5A, 15A, 30A and 45A.
​Determine which one of the fuses is suitable for the house.
K.C.S.E Physics Q & A - MODEL 2002PP1QN27
Cobalt 60 is a radio isotope that has a half – life of 5.25 years. What fraction of the original atoms in a sample will remain after 21 years?
answer
K.C.S.E Physics Q & A - MODEL 2002PP1QN16
The chart below shows an arrangement of different parts of the electromagnetic spectrum
​Name the radiation represented by A.
answer
K.C.S.E Physics Q & A - MODEL 2001PP2QN05
​a) You are provided with 12V a.c source, four diodes and resistor.
i) Draw a circuit diagram for a full wave rectifier and show the points at which the output is taken. AC source shown-symbols; arrangement of diode (one for each pair); correct position of R; correct position of output. ii) Sketch the graph of the output when a capacitor is put in parallel with the resistor in the circuit in (i) above.
​b) A certain transistor is connected in common-emitter-mode. The base current IB is 0.50 ma. Determine the values of the:
(i) Emitter current IE. (ii) Base-collector current gain beta (iii) Current gain alpha K.C.S.E Physics Q & A - MODEL 2001PP2QN04
Fig 3 shows the main features of a cathode ray tube (CRT) of a cathode ray oscilloscope (CRO)​
i) Describe how the electrons are produced in the tube.
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