K.C.S.E Physics Q & A - MODEL 2016PP2QN16
​Figure 8, shows a circuit that may be used to charge a capacitor.
(i) state the observation on the milliameter when the circuit is switched on:
(ii) explain the observation in (i) above. b)The circuit in figure 8 is left on for some time. State the value of p.d. across: (i) the resistor R; (ii) the capacitor C; (c) sketch the graph of potential difference (V) across R against time. ​(d) Figure 9 shows three capacitors connected to a 10V battery
​Calculate:
(i) the combined capacitance of the three capacitors; (ii) the charge on the 5.0 uF capacitor.
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K.C.S.E Physics Q & A - MODEL 2016PP2QN15
Figure 15, shows two coils A and B placed close to each other. A is connected to a steady D.C. supply and a switch, B is connected to a sensitive galvanometer.
​i)The switch is now closed, state the observation made on the galvanometer.
ii)Explain what would be observed if the switch is then opened. b) The primary coil of a transformer has 1000 turns and the secondary coil has 200 turns. The primary coil is connected to a 240V ac. Mains supply. i) Explain how an e.m.f is induced in the secondary coil. ii)Determine the secondary voltage. iii) Determine the efficiency of the transformer given that the current in the primary coil is 0.20A and in the secondary coil it is 0.80A.
answers
(a) ​(i)The galvanometer will be deflected to one side and then back to zero.
(ii)A greater deflection will be obtained in the opposite direction as the current takes less time to die off than to build up b)(i)The changing current in the primary coil induces a current in the secondary coil due to changing magnetic field of the primary current ii)Ns/Np = Vs/Vp hence Vs = (240 x 200)/1000 = 48V iii)Efficiency = power output/Power input x 100 (4.8 x 0.8 x 100)/240 x 0.2= 80% K.C.S.E Physics Q & A - MODEL 2016PP2QN14
​Figure 6 shows a simple electric bell circuit
​(i)Name the parts labeled
(I) D (II) E (ii)When the switch is closed, the hammer hits the gong repeatedly. Explain why: (I) the hammer hits the gong. (II) the hammer hits the gong repeatedly. (b) An electric bulb is rated 60 W, 240 V. Determine: (i) the current that flows through it when it is connected to a 240 V supply. (ii) the resistance of the bulb. K.C.S.E Physics Q & A - MODEL 2016PP2QN13
​A boy standing in front of a cliff blows a whistle and hears the echo after 0.5s. He then moves 17 metres further away from the cliff and blows
the whistle again. He now hears the echo after 0.6s. Determine the speed of the sound. K.C.S.E Physics Q & A - MODEL 2016PP2QN12
.When germanium crystal is doped with arsenic, it becomes an N-type semiconductor. Explain how this change occurs.
(Number of electrons in the outermost shell for germanium =4, arsenic =5)
answer
K.C.S.E Physics Q & A - MODEL 2016PP2QN11
​A heater of resistance R1 is rated P watts, V volts while another of resistance R2 is rated 2P watts, V/2 volts. Determine R1 / R2
K.C.S.E Physics Q & A - MODEL 2016PP2QN10
​Figure 6 shows a narrow beam of X-rays passing between two metal plates in air. The plates are connected in series with a switch, a cell and a milliameter.
​It is observed that when the switch is closed a current flows in the milliameter. Explain this observation.
answer
K.C.S.E Physics Q & A - MODEL 2016PP2QN09
Draw a ray diagram to show how a ray of light may be totally internally reflected two times in an isosceles right - angled glass prism.(Assume that the critical angle of glass is 42
K.C.S.E Physics Q & A - MODEL 2016PP2QN08
​The following is part of radioactive decay series
​Determine the values of a and b
answers
​a = 234
b= 82 K.C.S.E Physics Q & A - MODEL 2016PP2QN07
​Figure 5 shows the cross-section of a dry cell. Use the information on the figure to answer questions below
​(a) Name the parts labeled A and B.
(b) State the use of manganese (IV) oxide in the cell.
answers
​(a) A – Carbon rod or graphite rod
B – Mixture of Manganese (IV) oxide with carbon powder (b) Manganese (IV) oxide is a depolarizer or oxidizing agent. It is used to oxidize hydrogen to water K.C.S.E Physics Q & A - MODEL 2016PP2QN06
​Figure 4 shows straight waves incident on a diverging lens placed in a ripple tank to reduce its depth
​Complete the diagram to show the waves in both the shallow region and beyond the lens.
K.C.S.E Physics Q & A - MODEL 2016PP2QN05
​State the reason why a convex mirror is preferred over a plane mirror for use as a driving mirror.
answer
K.C.S.E Physics Q & A - MODEL 2016PP2QN04
​Figure 5, shows how the displacement of a point varies with time as a wave passes it.
​On the same diagram, draw a wave which passes the point with half the amplitude and twice the frequency of the one shown.
K.C.S.E Physics Q & A - MODEL 2016PP2QN03
​Figure 4 shows a solenoid carrying an electric current.
​Sketch the magnetic field pattern inside and at the ends of the solenoid
K.C.S.E Physics Q & A - MODEL 2016PP2QN02
.An un-magnetized steel rod is clamped facing North-South direction and then hammered repeatedly for some time. When tested, it is found to be magnetized. Explain this observation. ​
answer
K.C.S.E Physics Q & A - MODEL 2016PP2QN01
​Figure 1 shows a ray of light incident on a mirror at an angle of 45°.Another mirror is placed at an angle of 45° to the first one as shown.
​Sketch the path of the ray until it emerges.
K.C.S.E Physics Q & A - MODEL 2015PP2QN18
​(a) Three resistors of resistance 2 ohms, 3 ohms and 4 ohms are to be connected to a cell such that they have the least effective resistance.
(I) Draw a circuit diagram to show how they can be connected to achieve this. (ii) Determine the least effective resistance of the three resistors.
​(b) A real object of height 1 cm placed 50 mm from a converging lens forms a virtual image 100 mm from the lens.
(i) Determine the: (I) focal length of the lens; (II) magnification. (ii) On the grid provided draw to scale the ray diagram for the set up, to show how the image is formed. K.C.S.E Physics Q & A - MODEL 2015PP2QN17
​(a) State three factors that affect the capacitance of a parallel plate capacitor.
(b) Figure 5 shows the circuit used to charge a capacitor C
​(i) State what would be observed on the following when the switch is closed:
(I) the milliammeter; (II) the voltmeter; (ii) Explain how the capacitor gets charged. (iii) State the purpose of the resistor R. (iv) On the axes provided, sketch the graph of voltage (V) against time (t)
answers
​(a) distance of separation between plates
area of overlap of plates type of dielectric between plates (b) (i) (I) Current rises to maximum and then drops to zero (II) Potential difference between the plates increases to a maximum (ii) Negative charges flow from the negative terminal of the battery to one plate of the capacitor. Negative charges flow from the other plate of the capacitor to the positive terminal of the cell hence equal positive and negative charges gather on the plates, opposing further flow of electrons when fullycharged (iii) Resistor - to slow down the charging process so that current and voltage are is observed. K.C.S.E Physics Q & A - MODEL 2015PP2QN16
​(a) It is observed that alpha particles have a lower penetrating power than beta particles. Explain this observation.
(b) A radioactive substance has a half life of 12 years. Determine the time it would take to decay to 12.5% of its original value.
​(c) A Geiger Müller (GM) tube is used for detecting radiations from a radioactive source.
State the function of: (i) the mica window; (ii) bromine gas in the tube. (d) (i) In a diffusion chamber, explain why some of the tracks formed are observed to be; (I) Short, (II) Straight. (ii) State two advantages of using a GM tube instead of a diffusion cloud chamber to detect radiations from radioactive substances.
answers
(a) Alpha particles are heavier and move at lower speeds hence less penetrating power than
Beta particles which are lighter and move faster
​(c) (i) allows the radiations into the tube
(ii) absorbs kinetic energy of positive ions so that they do not cause secondary ionization in the tube (d) (i) Short - They ionize heavily loosing most of the energy hence cannot travel far. Straight - They are massive compared to air molecules hence collision with air molecules cannot change their path. (ii) GM is easily portable than a cloud chamber. GM is more sensitive. GM tube detects radiation at very low intensity and cloud chamber cannot detect radiation at very low intensity. K.C.S.E Physics Q & A - MODEL 2015PP2QN15
​.(a) State two factors that determine the resistance of a metallic conductor.
(b) Explain how a fuse safeguards electrical appliances against excessive currents.
​(c) A hair dryer is rated 2.5 kW, 240 V.
(i) Determine whether a 10 A fuse may be suitable for the hair dryer. (ii) Determine the cost of using the hair dryer for 3 hours if the cost of electricity is Ksh 0.80 per kilowatt hour. K.C.S.E Physics Q & A - MODEL 2015PP2QN14(a) State two factors that affect photoelectric emission.
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