Free KCSE Physics Topical Questions KNEC Standards

K.C.S.E Physics Q & A - MODEL 2007PP2QN17

15/7/2020

K.C.S.E Physics Q & A - MODEL 2007PP2QN17

(a) State Lenz's Law of electromagnetic induction
(b) Figure 13 shows a simple microphone in which sound waves from the person talking cause the cardboard diaphragm to vibrate

(i) Explain how a varying current is induced in the coil when the diaphragm vibrates
(ii) State two ways in which the induced current in (i) above can be increased
(c) A transformer with 1200 turns in the primary circuit and 120 turns in the secondary circuit has its primary circuit connected to a 400V a.c source. It is found that when a heater is connected to the secondary circuit, it produces heat at the rate of 600w. Assuming 100% efficiency, determine the:
(i) Voltage in the secondary circuit
(ii) Current in the primary circuit
(iii) The current in the secondary circuit

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K.C.S.E Physics Q & A - MODEL 2002PP2QN02

10/7/2020

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K.C.S.E Physics Q & A - MODEL 2002PP2QN02

Fig. 3. Shows the path of radiation form a radioactive source after entering a magnetic field. The magnetic field is directed into the paper and is perpendicular to the plane of the paper as shown in the figure

Identify the radiation
b) Below is a nuclear reactio

i) Identify radiation K
ii) Determine the values of X and Y.
(c) Fig 3 shows a device for producing metal foils of constant thickness. Any change in thickness can be detected by the Geiger tube and recorded by the Geiger. The pressure adjusted by the roller is then adjusted to keep the thickness constant.

(i) State the change in the metal foil that will lead to a decrease in the Geiger counter reading
(ii) Give a reason for your answer in c(i) above
(iii) State the change in the roller pressure that should be made as a result of this decrease in the Geiger counter reading.
(iv) Give a reason for your in (c) (iii) above
(v) Explain why a source emitting (alpha) particles only would not be suitable for this device.
(vi) Explain why a radioactive source of a half-life of 1600 years is more suitable for use in the device than one of a half-life of 8 minutes.

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K.C.S.E Physics Q & A - MODEL 1998PP1QN20

6/7/2020

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K.C.S.E Physics Q & A - MODEL 1998PP1QN20

Table 1 carries information on the type of radiation, detector and use for some of the electromagnetic radiations. Fill in the blanks.

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Heating/ cooking/communication/eye/photographic film or plate/LDR/photocell

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K.C.S.E Physics Q & A - MODEL 1995PP1QN29&30

3/7/2020

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K.C.S.E Physics Q & A - MODEL 1995PP1QN29&30

In an experiment on photo- electricity using metal X, the graph shown in figure 9 was obtained. Use the graph to answer questions 29 and 30.

(a)Determine the minimum frequency f0 below which no photoelectric emission occurs
(b) Sketch on the same axes, a graph for a metal, Y hose work function is higher than metal X

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