PAPER 2 THEORY QUESTIONS

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Geoffrey Butler
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1 PAPER 2 THEORY QUESTIONS 1 A plastic rod is rubbed with a cloth and becomes negatively charged. (a) Explain how the rod becomes negatively charged when rubbed with a cloth... [2] (b) An uncharged metal-coated sphere hangs from an insulating thread. The sphere is brought near to the rod. The sphere is attracted to the rod, as shown in Fig.1.1. Fig. 1.1 (i) Describe and explain what happens to the free electrons in the metal-coated sphere as it approaches the rod....[2] (ii) Draw a diagram to show how charge is distributed on the sphere. [1] (iii) Explain why the uncharged sphere is attracted to the negatively-charged rod....[2] (c) With the charged rod still close, point X on the metal-coated sphere is earthed. (i) State what is meant by earthing the sphere....[1] (ii) Describe and explain what happens to the free electrons in the metal-coated sphere as itis earthed....[2] (iii) Draw a diagram to show how the charge is now distributed on the sphere. [1] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 1

2 (d) Describe one device where electrostatic charging is used. In your answer include a diagram and explain how and why the charge is produced... [4] 2 Two conducting spheres are rubbed and become charged, as shown in Fig.2.1. Fig. 2.1 (a) The spheres are uncharged before they are rubbed. Explain, in terms of the movement of electrons, how they become charged... [1] (b) On Fig. 2.1, draw the electric field pattern between the spheres. Show the direction of the field lines. (c) A metal wire is used to connect the two spheres together. In a time of 2.0 x 10 3 s, a charge of 1.8 x C passes through the wire. Calculate the current in the wire. Current = [2] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 2

3 3 Some electrical components are easily damaged if electric charge is placed on them. They are often stored by placing them in connect with a conductor. (a) When the component shown in Fig.3.1 is rubbed with a cloth, the metal legs become negatively charged. Explain how this happens. Fig. 3.1 (b) Fig.3.2 shows the negatively charged metal legs placed near a piece of aluminium foil which rests on an isolator. Fig. 3.2 (i) On Fig.3.2, draw the induced charges that form on the aluminium foil. (ii) The metal legs are placed in contact with the aluminium foil. Describe what happens to the charges on the foil and on the legs. 4 Two vertical metal plates are connected to a high voltage power supply, shown in Fig.4.1. An electric field exits in the space between the plates. Fig. 4.1 (a) (i) State what is meant by the electric field between the plates. (ii) On Fig.4.1, draw lines of force to show the electric field between the plates. MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 3

4 (b) An uncharged metal ball is hung by an insulating thread between the two, plates as shown I Fig.4.2. On Fig.4.2, Fig. 4.2 (i) draw the distribution of charge that will be found on the metal ball, (ii) draw lines of force to show the new electric field between the plates. 5 One method of painting a metal panel uses electrostatic charges. A paint spray produces paint droplets, all of which are given a positive charge. The metal panel is given a negative charge, as shown in Fig Fig. 5.1 (a) State the effect that charges have on each other. (i) like charges... (ii) unlike charges...[1] (b) (i) Explain why the droplets spread out as they leave the nozzle in Fig. 5.1 (ii) Explain why it is important that the metal panel has a negative charge.... [2] (c) State one advantage of using electrostatics in this way to paint the metal panel... [1] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 4

5 7 Electrostatic charges can be placed on objects by friction. (a) State the name of the charged particle that is transferred from one object to another in this process. (b) Fig. 6.1 shows petrol (gasolene) being pumped into a can. Electrostatic charges build up on the petrol and the pipe. (i) Explain why this is dangerous. Fig. 6.1 (ii) State what can be done to stop the electrostatic charge building up in this way. 7 (a) An aeroplane becomes positively-charged as it flies through the air, because it loses particles from its metal surface. (i) State the name of the particles lost from the metal surface.... [1] (ii) The tyres of the aeroplane are made from an electrical conductor. Explain what happens to the charge on the aeroplane when it lands.... [2] (b) Suggest why it is necessary to keep an aeroplane connected electrically to earth during refuelling... [2] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 5

6 8 Three cells are connected in series making a battery, as shown in Fig The e.m.f. of each cell is 1.5 V. A resistance of 15Ω is connected to the battery. (a) What is the total e.m.f. of the battery.. [1] (b) Calculate the current in the circuit. State the equation that you use. Fig. 8.1 current =... [3] (c) A battery can be made from cells connected in parallel, as shown in Fig Fig. 8.2 State one advantage of connecting the cells in parallel... [1] 9 Fig.9.1 shows three combinations of resistors connected between points X and Y. All the resistors have resistance 6.0Ω. Fig. 9.1 MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 6

7 (a) Calculate the total resistance between the points X and Y of each combination. (i) combination A (ii) combination B total resistance of combination A = (iii) combination C total resistance of combination B = total resistance of combination C = [4] (b) Points X and Y in combination B are connected to a battery that provides a p.d. of 1.35V across XY, a shown in Fig.9.2. Calculate the currents I 1, I 2 and I 3 in each resistor of the combination. Fig. 9.2 I 1 = I 2 = I 3 =. [3] 10 Fig shows a circuit in which a voltmeter is placed across a resistor. Fig MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 7

8 The potential difference across the 12Ω resistor is 4.0 V. The voltmeter has three different ranges: 0 to 3.0 V, 0 to 6.0 V and 0 to 30 V. The best range for use in this circuit is 0 to 6.0 V. (a) Explain why (i) using the voltmeter on the range 0 to 3.0 V is unsuitable, (ii) using the voltmeter on the range 0 to 30 V is unsuitable.... [2] (b) (i) Calculate the current in the 12Ω resistor. State the formula that you use. (ii) Calculate the p.d. between A and B in Fig current = p.d. =. [5] 11 Fig shows an electrical circuit containing a 12 V power supply and a number of resistors. (a) Calculate the combined resistance of (i) the 2 Ω and 4 Ω resistors in series, (ii) the 3 Ω and 6 Ω resistors in parallel. Fig resistance =... [1] resistance =... [2] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 8

(b) Calculate the reading of the ammeter in Fig.11.1. (c) Determine the potential difference across the 4 Ω resistor. ammeter reading =... [2] p.d. =... [2] 12

9 (b) Calculate the reading of the ammeter in Fig (c) Determine the potential difference across the 4 Ω resistor. ammeter reading =... [2] p.d. =... [2] 12 Fig shows how the currents in a lamp L and in a wire W vary with the potential difference (p.d.) applied. Fig (a) (i) Draw a diagram of the circuit that you would use to take the readings of current and p.d. for the lamp. State the range you would choose for the voltmeter. [5] (ii) Describe how the resistance of the lamp L varies as the p.d. increases.... [1] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 9

10 (b) (i) Fig shows the lamp L and the wire W connected in series. The current in the circuit is 0.8 A. Fig Determine, using the graph or by calculation, 1. the p.d. across L, 2. the p.d. across W, 3. the p.d. of the supply, 4. the resistance of the lamp L in Fig (ii) Fig shows the lamp and wire connected in parallel. A p.d. of 12 V is connected across them. [5] Fig Determine, using the graph or by calculation, 1. the current IW in the wire W, 2. the current IL in the lamp L, 3. the total current I in the circuit, 4. the resistance of the wire W. [4] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 10

11 13 A filament lamp is labelled 240 V, 0.20 A. (a) Calculate the resistance of the lamp at normal brightness. resistance =... [2] (b) The lamp is connected to a 240 V supply and switched on at time t = 0. Fig shows the variation with t of the resistance of the lamp. Fig Describe how the current in the lamp varies with t... [2] (c) A second filament lamp has higher resistance. State two differences between the two filaments that may cause the change in resistance 1 The filament in the second lamp is The filament in the second lamp is......[2] 14 (a) Describe an experiment to show the difference between an electrical insulator and an electrical conductor. Name one example of each. [4] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 11

12 (b) Fig is a sketch graph of the current in a component P against the potential difference (p.d.) across it. (i) Fig Define resistance.... [1] (ii) State how the resistance of P varies with the p.d. across it.... [1] (iii) Suggest what component P is.... [1] (iv) Explain why the resistance of P varies with the p.d. across it.... [2] (c) Component P is used in the electrical circuit shown in Fig Fig The current in ammeter 2 is 0.40 A and the current in ammeter 3 is 0.60 A. (i) Determine the readings of ammeters 1 and 4. readings of ammeters 1 and 4 =. [1] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 12

13 (ii) Calculate the p.d. across the 20 Ω resistor. p.d. =.. [2] (iii) State the p.d. across the power supply. p.d. =.. [1] (iv) Calculate the resistance of P in this circuit. resistance =.. [1] 15 A motorcycle battery consists of six 2.0 V cells in series. The battery supplies energy to the headlight. (a) State the total electromotive force (e.m.f.) of the battery... [1] (b) The motorcycle headlight contains two identical filament lamps F and G. Filament lamp F is always lit but filament lamp G is turned on and off by switch D. Fig is the circuit diagram. Fig When switch D is open, the battery supplies a current of 4.6 A. Complete the table of Fig Fig MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 13

14 (c) Calculate the energy supplied by the battery as an electric charge of 200 C moves through the circuit. energy supplied =... [2] 16 Fig shows a 9.0 V battery connected in series with a 16.0 Ω resistor and a small metal conductor X at room temperature. Fig A voltmeter measures the potential difference (p.d.) across the 16.0 Ω resistor. At room temperature the resistance of X is 4.0 Ω. (a) (i) Calculate the current supplied by the battery. (ii) Calculate the p.d. across the 16.0 Ω resistor. current =... [2] p.d. =... [1] (b) X is heated slowly to a very high temperature. (i) Sketch a graph to show how the resistance of a metal conductor depends on its temperature. [2] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 14

15 (ii) State and explain how the voltmeter reading changes as the temperature of X rises.... [2] (iii) Suggest a suitable range for the voltmeter.... [2] 17 Fig shows a circuit 15V battery connected to the series with component X and 1500Ω resistor. X (a) On Fig. 17.1, draw an arrow at A to show the direction of flow of the electrons in the wire. [1] (b) What is the name of component X?.. [1] (c) State and explain how the potential difference across X varies as the light shining on it becomes brighter... [2] (d) In the darkness the resistance of the X is 3500Ω. Calculate (i) Fig the ammeter reading in the circuit. (ii) the voltmeter reading in the circuit. ammeter reading = [2] voltmeter reading = [2] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 15

16 18 (a) Describe an experiment, including an ammeter and a voltmeter, to show how the resistance of a wire varies with temperature. Draw a circuit diagram [4] (b) The filament in a lamp is made from metal wire. (i) Describe the variation with temperature of the resistance of the filament lamp.... [2] (ii) On Fig. 18.1, sketch a graph of the variation of the current in the filament against the potential difference (p.d.) across it. Fig (c) Fig is a circuit used to monitor changes in room temperature. Fig MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 16

17 Thermistor is connected in series with a 6.0 V battery and a 2000 Ω resistor. (i) The temperature of the room increases. State and explain what happens to 1 the reading on the ammeter, 2 the reading on the voltmeter.. [4] (ii) At a certain temperature, the reading on the voltmeter is 3.8 V. Calculate the resistance of the thermistor at this temperature. resistance =... [3] 19 An electrical engineer measures the potential difference across a length of metal wire and the current in the wire. He does this for different values of the current. (a) (i) Draw a labelled circuit diagram of a circuit that enables the engineer to do this. [3] (ii) Describe how the circuit is used.... [2] (iii) State the equation that defines resistance.... [1] (b) The engineer performs the experiment and notices that the potential difference across the wire is directly proportional to the current in it. He calculates the resistance of the wire and plots a graph of the resistance against the current. On Fig. 19.1, sketch the shape of this graph. MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 17

18 20 At night, a bright floodlight is used to illuminate a building. The floodlight is a metal filament lamp. It is connected in series with a variable resistor and a 230 V mains power supply. When the floodlight is first switched on, the resistance of the variable resistor is at its maximum value. In the following few minutes the variable resistor is adjusted so that its resistance decreases slowly to zero. This causes the brightness of the lamp to increase until it reaches a maximum. At maximum brightness, the current in the lamp is 12 A. (a) Calculate the resistance of the lamp at maximum brightness. resistance =... [2] (b) State and explain what happens to the resistance of the lamp as its brightness increases... [2] (c) Suggest how, by using the variable resistor in this way, the filament lamp is protected from damage... [2] 21 (a) A lamp is marked 24 V, 100 W. Describe an experiment to check that the electrical power supplied to the lamp is 100 W when the potential difference (p.d.) across it is 24 V. In your account you should include a circuit diagram, state the readings that are taken, show how the result is calculated from the readings... [4] (b) Two lamps are connected in parallel to a 240 V mains supply, as shown in Fig Fig MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 18

19 Lamp A has a resistance of 190 Ω and lamp B has a resistance of 380 Ω. (i) Calculate the current at points P, Q and R. P =.. Q = R = [3] (ii) Calculate the total resistance of the circuit. (c) Fig shows the same lamps connected in series to the mains supply. resistance =.. [2] (i) Calculate the current at point S. Fig (ii) Calculate the p.d. across lamp A. current =.. [2] p.d. =.. [2] (d) In a house, all lamps are connected in parallel to the mains supply, not in series. State and explain two reasons for this. In your explanation you may refer to the results of your calculations in (b) and (c)... [3] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 19

20 22 Fig shows an electric kettle. Fig (a) The body of the kettle is plastic but the outside casing of the heating element is metal. (i) Explain why a fuse is included in the circuit and explain what happens when the fuse blows....[3] (ii) Explain why the metal casing of the heating element is connected to earth....[2] (b) The electrical power input to the kettle is 2000W and the kettle is used for 6 minutes (0.1 hour). Calculate (i) the electrical energy, in J, supplied to the kettle. State clearly the formula that relates power, energy and time. energy = J [3] (ii) the electrical energy, in kw h, supplied to the kettle. energy = kwh [2] (iii) the cost of using the kettle if 1 kwh costs 8 cents. cost =. [2] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 20

21 23 Fig shows an electric kettle connected to the 240V mains supply by a flexible cable. The kettle has a power rating of 2500W. Fig The table shows the maximum current that may be carried safely by wires of various diameters. (a) Show that the current in the cable when the kettle is in use is 10.4 A. State clearly any equation that you use. current =.. [2] (b) (i) From the table, select the smallest diameter of wire that can safely be used for this kettle. (ii) Explain why it is dangerous to use a wire thinner than that in (i).... [3] (c) Describe one fault that may occur in the flexible cable that will cause the fuse in the plug to melt... [1] 24 Fig shows a mains extension lead. The six sockets allow several electrical appliances to be connected to the mains supply through one cable. Fig MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 21

22 (a) The cable connects the sockets to the mains supply. The cable contains three wires: live, neutral and earth. State what is meant by (i) live,... [1] (ii) neutral,... [1] (iii) earth.... [1] (b) Six powerful lamps are plugged into the sockets and switched on, one by one. (i) State what happens in the cable as the lamps are switched on, one by one.... [1] (ii) Describe why it can be dangerous when a fuse of the wrong value is used in the plug.... [1] (c) Explain why your hands should be dry when you put a plug into a socket... [1] 25 The owner of a house records the details of the electricity use of all the appliances during a day. The details are shown in Fig Fig (a) Complete Fig by calculating the energy used by each appliance. [2] (b) State which appliance has cost the most to use during the day.. [1] (c) The house has a meter to record the total electrical energy used. At the beginning of the day, the meter reading was kWh. Calculate the meter reading at the end of the day. meter reading =... [1] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 22

23 (d) The wires supplying electric current to the water heater are thicker than those supplying current to the lights. Explain why this is necessary... [2] 26 Fig shows a cable containing three wires coloured brown, blue and yellow/green, and a mains plug with the cover removed. Fig (a) Describe how to connect the cable and the three wires correctly and safely to the plug... [3] (b) The table lamp shown in Fig is made from plastic. It has only two wires in the cable to connect it to the plug. Fig The lamp has a power rating of 100W and is used with a 230 V supply. (i) Which wire, earth, live or neutral, is not needed in the cable for the lamp?. [1] (ii) Explain why the lamp is safe to use even though it has only two wires in the cable.... [2] (iii) Explain what is meant by a power rating of 100W.... [2] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 23

24 (iv) Calculate the value of the fuse that should be used in the plug for this lamp. (v) Calculate the electrical energy supplied to the lamp in 30 minutes. fuse rate = [3] 27 Fig.27.1 shows a wiring diagram for two different lamps A and B. energy = [3] (a) State the names of components C and D and explain the purpose, in this circuit, of each of these components... [4] (b) When both lamps are working correctly, the current in C is 0.42 A. Lamp A is marked 240 V, 60W. Calculate (i) the current in lamp A, Fig (ii) the current in lamp B, current = [2] current = [2] (iii) the resistance of lamp A. resistance = [3] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 24

25 (c) The two lamps in Fig are connected in parallel. When wiring the circuit in a house, an electrician makes a mistake and connects the two lamps in series to the mains supply. He switches them on. (i) Draw a circuit diagram showing the two lamps connected in series to the mains supply. (ii) State whether the current in the two lamps is larger than, the same as, or smaller than the currents you have calculated in (b). Explain your answer.... [2] (d) Another lamp is made using the same material for the filament as lamp A. The filament in this new lamp has the same length as the filament in lamp A but has half the cross-sectional area. State the resistance of the new lamp... [1] 28 A microwave oven is rated at 650 W and is connected to a 230 V mains supply. (a) (i) Calculate the current from the supply when the microwave oven is switched on. (ii) Suggest a rating of the fuse for use with this oven. current =... [2] fuse rating =... [1] (b) The insulation of the mains cable has worn away. The live wire touches the outer metal casing of the microwave oven. (i) Explain the hazard that results if the outer metal casing is not earthed.... [2] (ii) Explain how connecting the earth wire to the outer casing and using a fuse of a suitable rating removes this hazard.... [2] 29 The cable from the mains plug to a washing machine contains a live wire, a neutral wire and an earth wire. The earth wire is connected to the metal case of the washing machine. (a) Explain how connecting the earth wire to the metal case makes the washing machine safer... [2] (b) When in use, the average input power to the washing machine is 500 W. Calculate the number of kw h of energy used by the washing machine in 45 minutes of use. number of kw h =...[2] MS / Sh.M / FT12 / Gr 10 / physics / Theory questions / Electricity 25

ELECTRICITY & MAGNETISM - EXAMINATION QUESTIONS (4)

ELECTRICITY & MAGNETISM - EXAMINATION QUESTIONS (4) 1. Which two electrical quantities are measured in volts? A current and e.m.f. B current and resistance C e.m.f. and potential difference D potential