9 (a) Diagram 9.1 shows the pattern of magnetic field formed when current flows in a coil.The magnetic field strength is greater at the center compared to the edge

(a) (i) What is meant by magnetic field? [1 mark]

(ii) Explain why the strength of the magnetic field is greater at the center[3 marks]

(b) Diagram 9.2 and Diagram 9.3 show the the magnetic field produce when currentflows in a conductor.Diagram 9.4 shows the magnetic field produced when current carrying conductors inDiagram 9.2 and Diagram 9.3 is placed in magnetic field

(i) Based on Diagram 9.2 and Diagram 9.3, compare the- pattern of the magnetic field- direction of the magnetic field

[2 marks](ii) Based on Diagram 9.2 ,Diagram 9.3 and 9.4 compare the pattern of the magnetic field

[1mark](iii) Based on Diagram 9.4 compare the direction of the resultance forces

[1mark]

(iv) Name one instrument which uses the same principle as in Diagram 9.4.Explain the similarities.

[2 mark](c) Diagram 9.5 shows a moving coil loudspeaker.

You are required to give some suggestions to design a moving loudspeaker which isfunctional and can produce loud sound.Using the knowledge on electromagnet, forces and the properties of materials, explain thesuggestions based on the following aspects ;(i) the shape of the magnet(ii) the position of the coil(iii) material used for the cone(iv) type of electrical supply(v) material used for the body of the loudspeaker

[10 marks]Mark Scheme

11 a) Diagram 11.1 (a) shows a filament bulb labeled “240 V. 80 W”.Diagram 11.1 (b) shows a graph of potential difference against current for two materials, Y and Z.One of the materials will be chosen as filament in a bulb.

i) What is meant by “240 V, 80 W?”[1 mark]

ii) Based on the graph in Diagram11.1 (b), compare the resistance of materials Y and Z.Choose the more suitable material to use as a filament of the bulb. Explain your choice.

[4 marks]b) As a researcher, your duty is to study the characteristics of a material to make a heating element ofa water heater. You are given four choices of heating elements J, K, L and M. Table 1 shows thecharacteristics of the four heating elements.

You are required to determine the most suitable heating element.Study thespecifications of all the four metals based on the following aspects.- The cross sectional area- Melting point- Specific Heat Capacity- Length of the heating element

[10 marks]c) Three resistors with resistance 1 Ω, 2Ω, and 3Ω respectively are connected to 6 V battery asshown in Diagram 11.2.

Based on Diagram 11.2Calculate (i) Effective resistance (ii) Power dissipated by 2Ω resistor

[5 marks]Mark Scheme

1 Diagram 1 shows an electric circuit which is used to investigate the relationship between

electric current and potential difference across a conductor XY

(a) What is the function of the voltmeter? ………………………………………………………………………………………….

[1mark](b) Underline the correct answer in the bracket to complete the sentence below. When the electric current increases, (i) the potential difference (increase, decrease, remains unchanged)

[1mark](ii) the resistance will (increase, decrease, remains unchanged)

[1mark] (c) State one physical quantity which is kept constant in the experiment. ………………………………………………………………………………………….

[1mark]Mark Scheme

8 Diagram 8 shows a galvanometer with a resistance of 5Ω and a full-scale deflection of 5 mA.

The galvanometer uses the interaction between a permanent magnet and an electromagnet to measure a small current. The coil of the galvanometer gets heated up quickly, thus affecting

the reading shown by the pointer.(a) What is meant by electromagnet? …………………………………………………………………………………………...

[1 mark]Table 8 shows the specifications of four galvanometers J, K, L and M.

(b) Based on Table 8, state the suitable specifications for the coil and the core to make thegalvanometer more efficient. Give the reason for the suitability of the aspects.(i) Wire used for the coil…………………………………………………………………………………… Reason……………………………………………………………………….……………

[2 marks](ii) Core material……………………………………………………………………………………. Reason…………………………………………………………………………………….

[2marks](iii) Number of turns of the coil…………………………………………………………………………………..… Reason…………………………………………………………………………………….

[2marks] (c) Based on the answers in 8(b), determine the most suitable galvanometer in Table 8 to measure a small current. ……………………………………………………………………………………..

[1marks] Mark Scheme

10. (a) Diagram 10.1 and Diagram 10.2 show the relative motion between the magnetand solenoid. Ends of the coils are connected to a centre-readinggalvanometer.

Using Diagram 10.1 and Diagram 10.2, compare: (i) the direction of the movement of the magnet (ii) the deflection of the galvanometer pointer (iii) Relate the movement of the magnet, the polarity at the top of the coiland the force acts on the magnet to deduce a relevant physics law.

[5 marks](b) Name the physics law that describes the observations in Diagram 10.1 andDiagram 10.2.

[1 mark](c) Diagram 10.3 shows a direct current generator

Explain how the above generator works to produce direct current.[4 marks]

(d) Diagram 10.4 shows a cross section of a moving coil microphone. Amicrophone converts one form of energy into another

When the diaphragm moves in response to sound, the attached coil moves inthe magnetic field and generates a very small current in the wire of the coil.Using an appropriate concept in physics, suggest and explain suitablemodifications or ways to enable the microphone to detect sound effectivelyand generate bigger current based on the following aspect:(i) thickness of diaphragm (ii) strength of the material for diaphragm (iii) number of turns of coil (iv) diameter of the wire of coil (v) strength of magnet

[10 marks]Mark Scheme

8 Diagram 8.1 shows an electric kettle with specification of 240 V, 1.2 kW.

(a) What is meant by the label 240V, 1.2 kW?…………………………………………………………………………………………………..

[1 mark](b) Calculate (i) the current flows through the electric kettle.

[2 marks](ii) the resistance of the heating elements in the kettle.

[2 marks](c) Four electric kettles W, X , Y and Z with specification 240 V, 2 kW are made from the

materials with different characteristics.Table 8.1 shows the characteristics of the materials.

(i) Based on the characteristics of the heating elements in Table 8.1, suggest two electric kettles are suitable to heat water. Give the reason for your answer.…..……………………………………………………………………………………..…..……………………………………………………………………………………....………………………………………………………………………………………....………………………………………………………………………………………..

[3 marks](ii) Based on the fuse used in the Table 8.1 , suggest two electric kettles are suitable to heat water. Give the reason for your answer...………………………………………………………………………………………....………………………………………………………………………………………..

[2 marks](iii) Using your answer in (b)(i) and (b)(ii), suggest which electric kettle is the most suitable to heat water. Give the reason for your answer.…..……………………………………………………………………………………..…………………..……………………………………………………………………..

[2 marks]Mark Scheme

5. The label on electric kettle is marked 240 V , 3 kW. The kettle contains 1.7 kg of water at 200 C. It takes 3.5 minutes to raise the temperature of the water to 1000C.[ Specific heat capacity of water is 4.2 X103J kg-10C-1

specific latent heat of vaporization of water 2.3 X106J kg-1]

(a) What is meant by specific heat capacity?………………….………………………………………………………..…………………………………………………………………………..

[ 2 marks ] (b) Calculate (i) the energy output of the electric kettle in 3.5 minutes,

[ 2 marks ](ii) the energy required to raise the temperature of 1.7 kg of water from 200C to 1000C.

[ 2 marks ](iii) the energy required to boil away 0.23 kg of water at 1000C.

[ 2 marks ]Mark Scheme

10. Diagram 10.1 shows a current carrying conductor in a magnetic field and the direction of current flow is as shown.

(a) Based on diagram 10.1, (i) draw the resultant magnetic field when the current carrying conductor is placed in the permanent magnetic field.(ii) show the direction of the force on the current carrying conductor.(iii) in which direction - K, L, M and N will the conductor move?

[5 marks] (b) Diagram 10.2 shows the position of a copper wire PQ when the switch is off. Diagram 10.3 and Diagram 10.4 show the positions of a copper wire PQ when the switch is on in various strength of magnetic field.

Based on Diagram 10.2, Diagram 10.3 and Diagram 10.4, (i) what happens to the copper wire PQ when the switch is turned on?

[1 mark] (ii) compare the distance between the copper wire PQ and the plastic holder in Diagram 10.3 and Diagram 10.4.

[1 mark ] (iii) compare the strength of magnadur magnets in Diagram 10.3 and Diagram 10.4.

[1 mark ] (iv) relate the distance between the copper wire PQ and the plastic holder with the strength of the magnets.

[1 mark ] (v) hence, relate the force produced in the copper wire PQ with the the strength of magnets.

[1 mark ]

(c) Diagram 10.5 shows the basic structure of a moving coil ammeter. Suggest modifications that can be made to the meter so that it has the following characteristics:(i) Uniform scale. (ii) High sensitivity. (iii) The pointer is easily returned to zero when there is no current flow.

[10 marks ]Mark Scheme

2. (a) State Fleming’s left hand rule.[2 marks]

(b) From the aspect of the component and the working principle, state the difference between aD.C motor and an A.C dynamo.

[3 marks](c)

The magnetic flux, the current and the number of coils used in both the motors are thesame.Compare the shape of the magnet used in the 2 motors.Compare the efficiency of the 2 motors.Correlate the shape of the magnet used with the efficiency and deduce a relevant physicsconcept.

[5 marks](d) James buys a new bigger fishing boat. When he transfers the motor from his previousfishing boat to the new boat, he finds that the power of the motor is low. But he has no moremoney to buy a new motor. He decides to modify the old motor by using new magnetic coiland replaced the permanent magnet with a electromagnet.Based on the 2 ideas of James, suggest modifications can be done by him to upgrade thepower of the old motor.

[10 marks]Mark Scheme