K.C.S.E Physics Q & A - MODEL 2012PP2QN014
(a) Figure 12, shows a displacement - time graph for a progressive wave.
(i) state the amplitude of the wave.
(ii) determine the frequency of the wave. (iii) given that the velocity of the wave is 20m/s,determine its wavelength. (b) Figure 13 shows two identical dippers A and B vibrating in water in phase with each other. The dippers have the same constant frequency and amplitude, The wavesproduced are observed along line MN:
It is observed that the amplitudes are maximum at points Q and S, and minimum at points P and R.
(i) explain why the amplitude is maximum at Q. (ii) state why the amplitude is minimum at R. (iii) State what would happen if the two dippers had different frequencies.
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K.C.S.E Physics Q & A - MODEL 2012PP2QN013
Figure 11, shows an alternating current (a.c) connected across a diode D and a resistor R.
On the axes provided sketch the output as observed in the CRO connected across R.
State why alternating current (a.c) is used for transmitting electricity over long distances21/7/2020
K.C.S.E Physics Q & A - MODEL 2012PP2QN012
State why alternating current (a.c) is used for transmitting electricity over long distances
answer
K.C.S.E Physics Q & A - MODEL 2012PP2QN11
Figure 10, shows the cross section of a conductor held between two magnets and carrying a current out of the paper.
Indicate with an arrow on the diagram the direction in which the conductor will move when it is released.
K.C.S.E Physics Q & A - MODEL 2012PP2QN10
Figure 9, shows the cross-section of an optical fibre made of two types of glass A and B. The refractive index of B is lower than that of A.
A ray of light enters the optical fibre at P and emerges from Q.
(i) Sketch the path of the ray through the fibre. (ii) State the reason why light travels through the fibre as in (i) above. K.C.S.E Physics Q & A - MODEL 2012PP2QN09
Figure 8, shows an object O placed infront of a diverging lens whose principal focus is F
On the figure, draw a ray diagram to locate the image formed.
K.C.S.E Physics Q & A - MODEL 2012PP2QN08
Light from a lamp falls on the cap of a negatively charged electroscope. It is observed that the divergence of the leaf decreases. Explain the observation.
ANSWER
K.C.S.E Physics Q & A - MODEL 2012PP2QN07
Figure 7, shows two similar coils P and Q around the end L and M of a piece of soft iron. A steady current passes through the coils
State the polarity of the resulting magnet at end L.
ANSWER
K.C.S.E Physics Q & A - MODEL 2012PP2QN06
Figure 6, shows a narrow beam of radiation from a radioactive source, incident to a post card. The emergent radiation passes through a magnetic field which is perpendicular to the plane of the paper, and into the paper.
A detector moved along line AC only detects radiations B and C. State the types of radiation detected.
K.C.S.E Physics Q & A - MODEL 2012PP2QN05
Figure 5, shows an object O at the bottom of a beaker full of a liquid. An observer above the beaker sees its image at point X inside the liquid.
Determine the refractive index of the liquid.
K.C.S.E Physics Q & A - MODEL 2012PP2QN04
Figure 4, shows a negative point charge placed near a positively charged rod.
Draw on the diagram, the resulting electric field pattern.
K.C.S.E Physics Q & A - MODEL 2012PP2QN03
Figure 3, shows four identical light bulbs connected to a 15 volts battery whose internal resistance is negligible.
Determine the reading of the voltmeter V.
K.C.S.E Physics Q & A - MODEL 2012PP2QN02K.C.S.E Physics Q & A - MODEL 2012PP2QN01
Figure 1, shows a plane mirror XY placed equidistant from two parallel lines AB and PT.
Four students stand at P, Q, R and T in front of the mirror
(a) Indicate the positions of the images of students at Q, R and T on line AB. (b) State which of the images are visible to the student standing at P. (c) Using rays indicate on the figure, how (b) above is possible. K.C.S.E Physics Q & A - MODEL 2011PP2QN19
(a) When a radiation was released into a diffusion cloud chamber, short thick tracks were observed. State with a reason, the type of radiation that was detected.
(b) The half-life of an element X is 3.83 days. A sample of this element is found to have an activity rate of 1.6 x 103 disintegrations per second at a particular time. Determine its activity rate after 19.15 days. (c) State what is meant by an extrinsic semiconductor. (d) Figure 12, shows a depletion layer in an unbiased p-n junction.
State how a battery can be used to make the depletion layer narrower.
(e) Figure 13, shows an incomplete circuit of a full wave rectifier
(I) Draw in the figure two more diodes to complete the circuit.
(ii) Show on the figure the points across which the output of the rectifier should obtained. K.C.S.E Physics Q & A - MODEL 2011PP2QN18
(a) State two differences between cathode rays and electromagnetic radiations.
(b) Figure 10, shows the main features of a cathode ray oscilloscope (CRO)
(i) Name the parts labelled M and N.
M N (ii) Explain how electrons are produced in the tube. (iii) When using the CRO to display waveforms of voltages, state where the following should be connected: (I) the voltage to be displayed on the screen; (II) the time base voltage. (iv) state why the tube is highly evacuated. (c) Figure 11, shows the waveform of a voltage displayed on the screen of a CRO. The Y-gain calibration was 5V per cm.
(i) Determine the peak-to-peak voltage of the Y-input.
(ii) Sketch on the same figure the appearance of the waveform after the voltage of the input signal is halved and it’s frequency is doubled.
answers
(a) -Cathode rays have charge but e.m radiations don’t have charge;
-Cathode rays are particles and have a mass but e.m radiations are waves; -Cathode rays travel at a speed depending on the accelerating voltage but e.m radiations travel at the speed of light in vacuum; - Different in the mode of production. (b) (i) M - grid; N - accelerating anode/anode/vacuum; (ii) Cathode is heated by filament; electrons are released from cathode; by thermionic emission (iii) (I) across Y-Y plates. (Il) across X-X plates. (2 m (iv) to reduce collisions, (hence ionization) with air molecules in the tube. (c) (i) peak-to-peak voltage = 5 x 2 =10v K.C.S.E Physics Q & A - MODEL 2011PP2QN17
(a) State what is meant by the term “electromagnetic induction”.
(b) Figure 9, shows a simple electric generator
(i) Name the parts labelled P and Q.
P . Q (ii) Sketch on the axes provided, a graph to show how the magnitude of the potential difference across R, changes with the time t.
(iii) State two ways in which the potential difference produced by such a generator can be increased.
(c) In a transformer, the ratio of primary turns to the secondary turns is 1:10. A current of 500mA flows through a 200 ohms resistor in the secondary circuit. Assuming that the transformer is 100% efficient, determine: (i) the secondary voltage; (ii) the primary voltage; (iii) the primary current. K.C.S.E Physics Q & A - MODEL 2011PP2QN16
(a) State the meaning of the term “principal focus” as applied in lenses.
(b) You are provided with the following apparatus to determine the focal length of a lens: - a biconvex lens and lens holder. - alit candle. - a white screen. - a metre rule
(i) Draw a diagram to show how you would arrange the above apparatus to determine the focal length of the lens
(ii) Describe the procedure you would follow. (iii) State two measurements that you would take. (iv) Explain how the measurements in (iii) would be used to determine the focal length. (c) An object is placed 30cm in front of a concave lens of focal length 20cm. Determine the magnification of the image produced.
answers
(a) The point at which rays close to and parallel to the principal axis converge or seem to diverge from after striking the lens;
(ii) Candle is placed at a certain distance from the lens. The distance between the screen and the lens is adjusted until a sharp image is focused on screen.
(iii) The distance of candle from lens (U) is measured; The distance of screen from lens (V) is also measured; K.C.S.E Physics Q & A - MODEL 2011PP2QN15
(a) Figure 8, shows a graph of potential difference V (volts) against a current I (amperes) for a certain device.
From the graph:
(i) state with a reason whether or not the device obeys ohms law. (ii) determine the resistance of the device at: (1) 1 =l.5A (II) I =3.5A (iii) From the results obtained in (ii) state how the resistance of the device varies as the current increases. (iv) State the cause of this variation in resistance. (b) Three identical dry cells each of e.m.f. 1 .6V are connected in series to a resistor of 11.4 ohms. A current of 0.32A flows in the circuit. Determine: (i) the total e.m.f. of the cells; (ii) the internal resistance of each cell;
K.C.S.E Physics Q & A - MODEL 2011PP2QN14
State the meaning of the term “threshold frequency” as used in photoelectric emission.
answer
State the reason why electrical power is transmitted over long distances at very high voltages.20/7/2020
K.C.S.E Physics Q & A - MODEL 2011PP2QN13
State the reason why electrical power is transmitted over long distances at very high voltages.
answer
K.C.S.E Physics Q & A - MODEL 2011PP2QN12
Table I shows radiations and their respective frequencies.
Arrange the radiations in the order of increasing energy.
answer
K.C.S.E Physics Q & A - MODEL 2011PP2QN11
A 4 ohms resistor is connected in series to a battery of e.m.f 6V and negligible internal resistance. Determine the power dissipated by the resistor.
K.C.S.E Physics Q & A - MODEL 2011PP2QN10
Figure 7, shows two rays of light incident normally on face PQ of a glass prism, whose critical angle is 42°.
Complete the diagram to show the paths of the two rays as they pass through the prism.
K.C.S.E Physics Q & A - MODEL 2011PP2QN09
Figure 6, shows standing waves on a string. It is drawn to a scale of 1:5
(a) Indicate on the diagram the wavelength of the standing wave.
(b) Determine the wavelength of the wave. |
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