K.C.S.E Physics Q & A - MODEL 2007PP2QN18
​(a) Figure 14 shows the features of a cathode ray tube
​(i) Name the parts labeled A and B
A …………………………………. B……………………………. (ii) Explain how the electrons are produced in the tube (iii) State two functions of the anodes (iv) At what part of the cathode ray tube would the time be connected? (v) Why is a vacuum created in the tube? (b) The graph in figure 15 was obtained on a cathode ray oscilloscope (CRO) screen when the output of an a.c generator was connected to the input of the CRO. The time- base calibration of the CRO was set at 20 milliseconds per centimeter and the y- gain at 5 volts centimeter. 
​(i) Determine the pick voltage of the generator
(ii) Determine the frequency of the voltage On the same grid, redraw the graph for the same voltage when the time base calibration is set at 40 milliseconds per centimeter and y- gain at 10 volts per centimeter. (Show at least one complete cycle)
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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 2007PP2QN16
​(a) Figures 11 (a) and (b) show diagrams of the human eye
​(i) Sketch in figure 11 (a) a ray diagram to show shortsightedness
(ii) Sketch in figure 11 ( b) a ray diagram to show how a lens can be used to correct the shortsightedness (b) Figure 12 shows the features of a simple camer 
(i) Name the parts labeled A and B
A ………………………………………. B ………………………………………. (ii) A still object is placed at a certain distance from the camera. Explain the adjustments necessary for a clear image of the object to be formed. (iii) State the functions of the shutter and the parts labeled A and B Shutter …………………………………………………………………. A………………………………………………………………………… B ……………………………………………………………………….. (c) A lens forms a clear image on a screen when the distance between the screen and the object is 80cm. If the image is 3 times the height of the object, determine. (i) The distance of the image from the lens (ii) The focal length of the lens
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K.C.S.E Physics Q & A - MODEL 2007PP2QN15
​(a) State Ohm's Law
(b) The graph in figure 9 shows the current – voltage characteristics of a certain device, X 
(i) State with a reason whether the device obeys Ohm's law
(ii) Determine the resistance of the device, X, when the current through it is 60 mA. (iii) When the device, X is connected in the circuit below, the voltage across it is 0.70 V. 
​Calculate the value of the resistance R.
(c) The cell in figure 10 has an e.m.f of 2.1 V and negligible internal resistance. 
​Determine the
(i) Total resistance in the circuit (ii) Current in the circuit (iii) Reading of the voltmeter
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K.C.S.E Physics Q & A - MODEL 2007PP2QN14
​ You are provided with a diode, a resistor R, an a.c source of low voltage and connecting wires.
In the space provided, sketch the circuit diagram for a half – wave rectifier and indicate the terminals where the output voltage V0 may be connected. 
answer
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M.A NyamotiMy passion is to see students pass using right methods and locally available resources. My emphasis is STEM courses |
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