CIE iGCSE Co-Ordinated Science P4.3.2 Series and parallel circuits Exam Style Questions Paper 3
Question
(a) The two boxes on the left each contain the name of an energy resource.
The four boxes on the right contain advantages or disadvantages of the energy resources.
Draw two lines from each energy resource to the advantages or disadvantages of the energy resource.
(b) The statements, A to E, describe processes in a coal-burning power station.
They are not in the correct order.
A Coal burns to produce thermal energy.
B A turbine drives a generator.
C Steam is produced.
D Steam turns a turbine.
E Thermal energy boils water.
(i) Use the letters B to E to complete the sequence to describe how the power station generates electricity.
A $\underset{}{\rightarrow}$ …………. $\underset{}{\rightarrow}$ ………….$\underset{}{\rightarrow}$ ………….$\underset{}{\rightarrow}$ …………$\underset{}{\rightarrow}$ electricity is generated
(ii) State the boiling point of water.
(c) When coal is burned in a power station, the energy in the coal is transferred to the energy outputs shown in Table 9.1.
The energy outputs are shown as percentages of the total energy from the coal.
(i) Explain why Table 9.1 shows that energy is conserved in the processes in the power station.
(ii) The power station in Table 9.1 produces a lot of thermal energy.
Explain why the power station is not efficient.
(d) The electricity generated from the power station is supplied to a house to power the lighting circuit.
Lamps for lighting in the house are connected in a parallel circuit and not in a series circuit.
(i) Complete the circuit diagrams to show the difference between a series circuit and a parallel circuit.
Use two lamps in each circuit.
ii) State one advantage of connecting lamps in parallel in a lighting circuit.
▶️Answer/Explanation
Ans : 9(a) coal to non-renewable and polluting ;
geothermal to renewable and non-polluting ;
9(b)(i) A → E → C → D → B
E and C correct ;
D and B correct ;
9(b)(ii) 100(°C) ;
9(c)(i) numbers add up to a hundred ;
9(c)(ii) thermal energy is not useful / useful energy output is only 25% ;
9(d)(i) correct symbol for lamp ;
series circuit correct ;
parallel circuit correct ;
9(d)(ii) any one from :
all the lamps can be switched on independently
all lamps get full mains voltage
if one lamp fails the others can still work…
Question
(a) Fig. 6.1 shows an incomplete circuit diagram.
(i) Complete the circuit diagram in Fig. 6.1 by:
• adding an ammeter to measure the current in lamp A
• adding a voltmeter to measure the potential difference across lamp A.
(ii) Identify component X.
…………………………………………………………………………………………………………………….
(b) Lamp A has a resistance of 6.0Ω and lamp B has a resistance of 4.0Ω.
The current in lamp A is 1.2A.
(i) Calculate the potential difference across lamp A.
potential difference = ……………………………………………… V
(ii) Calculate the combined resistance of the two lamps connected in series.
resistance = ……………………………………………… Ω
(iii) The two lamps are now connected in parallel. Their combined resistance is different.
Identify from the list the combined resistance of the two lamps connected in parallel.
Explain your answer.
2.4Ω 4.0Ω 6.0Ω 10Ω 2 4Ω
combined resistance ……………………………………………………………………………………………
explanation …………………………………………………………………………………………………………
………………………………………………………………………………………………………………………….
(c) In lighting circuits in houses, lamps are connected in parallel.
State two advantages of using lamps connected in parallel rather than in series.
1 ………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
2 ………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
▶️Answer/Explanation
Ans: 6(a)(i) ammeter in series with lamp A completing the circuit ;
voltmeter across lamp A ;
both symbols correct ;
6(a)(ii) variable resistor ;
6(b)(i) p.d. = current × resistance (in any form) or 1.2 × 6.0 ;
= 7.2 (V) ;
6(b)(ii) 10.0 (Ω) ;
6(b)(iii) 2.4 (Ω) ;
resistance is less than the value of either individual resistance ;
6(c) any two from:
if one fails the other will still light ;
both lamps get full mains voltage ;
independent switching ;
Question
Fig. 9.1 shows a washing machine.
(a) (i) The washing machine uses:
• a heater to heat the water
• a motor to pump the hot water through the machine.
The motor and the heater are connected in a parallel circuit.
The motor and the heater are each operated by separate switches.
The circuit symbol for a heater is 
The circuit symbol for a motor is 
Fig. 9.2 shows an incomplete circuit diagram for the washing machine.
Complete the circuit diagram on Fig. 9.2.
(ii) The resistance of the heater is 20 Ω.
The resistance of the motor is 80 Ω.
Identify from the list the most likely value for the combined resistance of the heater and
motor connected in parallel.
Explain your answer.
16 Ω 20 Ω 50 Ω 80 Ω 100 Ω
combined resistance = …………………………. Ω
explanation …………………………………………………………………………………………………………
(iii) The current in the wires of the electrical circuit is a flow of charged particles.
State the name of the particles that flow in the wires of the electrical circuit.
(iv) The current-carrying coil in the motor experiences a turning effect.
This turning effect can be increased by increasing the number of turns on the coil.
State two other ways to increase this turning effect.
1 …………………………………………………………………………
2 …………………………………………………………………………
(b) Inside the washing machine, some of the water evaporates.
During evaporation, water changes state from a liquid to a gas.
(i) Complete the diagrams in Fig. 9.3 to show the arrangement and separation of molecules
in a liquid and in a gas.
(ii) During evaporation, the water does not boil.
State the boiling point of water.
…………………………………………….. °C
▶️Answer/Explanation
Ans : 9(a)(i) all symbols correct ;
heater and motor in parallel connection ;
switches correctly placed ;
9(a)(ii) 16 (Ω) ;
combined resistance in parallel is less than either individual resistance ;
9(a)(iii) electrons ;
9(a)(iv) increase current ;
increase strength of magnetic field ;
9(b)(i) liquid – all molecules touching random arrangement ;
gas – molecules widely separated (no more than seven shown) and random arrangement ;
9(b)(ii) 100 (°C) ;
Question
(a) Fig. 9.1 shows an electric circuit.
(i) When the switch is closed, ammeter A2 shows a reading of 0.6 A.
State the reading on ammeter A1.
………………………………………………. A
(ii) On Fig. 9.1, draw a voltmeter to measure the potential difference across lamp Y.
(b) Lamp X has a resistance of 2 Ω and lamp Y has a resistance of 4 Ω.
Calculate the potential difference across lamp Y.
State the unit of your answer.
potential difference = …………………………… unit ……………..
(c) An electric current transfers energy from the battery to the lamps.
(i) State two forms of energy emitted by filament lamps.
1 …………………………………………………………………………
2 …………………………………………………………………………
(ii) State the energy store in the battery (cells) that is decreasing when the circuit is switched on.
▶️Answer/Explanation
Ans : 9(a)(i) 0.6(A) ;
9(a)(ii) correct symbol ;
across lamp Y ;
9(b) PD = current x resistance (in any form) or 0.6 × 4 ;
= 2.4 ;
volts / V ;
9(c)(i) light ;
thermal ; (in either order)
9(c)(ii) chemical (potential) ;
Question
(a) A car has two headlamps, connected in parallel, across a 12V battery. There is one switch in the circuit which controls both lamps.
(i) Complete the circuit diagram in Fig. 9.1 to show how the two lamps and the switch are connected to the battery.
Fig. 9.1
(ii) The current passing through each lamp is 4.0A.
The potential difference across each lamp is 12V.
Calculate the resistance of each lamp.
State the unit of your answer.
resistance = …………………….. unit ……………….
(b) The car is crossing a long bridge.
Fig. 9.2 shows a gap in the road surface in the middle of the bridge.
On a hot day the temperature of the road surface increases.
(i) State what happens to the gap as the temperature increases.
…………………………………………………………………………………………………………………….
(ii) Explain why the gap is needed.
……………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………….
(c) The driver of the car notices that the sound from the engine is louder and has a higher pitch when the car accelerates up a hill.
(i) State how the amplitude of the sound wave changes when the car accelerates up the hill.
…………………………………………………………………………………………………………………….
(ii) State how the frequency of the sound wave changes when the car accelerates up the hill.
…………………………………………………………………………………………………………………….
(iii) The car gains thermal energy as it accelerates up the hill.
State two other forms of energy gained by the car as it accelerates up the hill.
1 ……………………………………………………………………………………………………………………
2 ……………………………………………………………………………………………………………………….
▶️Answer/Explanation
Ans: 9(a)(i) all symbols correct ;
two lamps in parallel with battery ;
switch to control both lamps ;
9(a)(ii) R = V/I (in any form symbols or words) or 12/4 ;
= 3 ;
ohms / Ω ;
9(b)(i) gap is smaller/closes ;
9(b)(ii) road/bridge needs to expand on hot day/
road/bridge could be damaged by expansion ;
9(c)(i) amplitude increases ;
9(c)(ii) frequency increases ;
9(c)(iii) kinetic (energy);
gravitational potential (energy) ;
Question(a)
A student constructs a circuit containing two lamps in parallel connected across two cells in series. Each lamp is controlled by a separate switch.
(i) Draw a circuit diagram for this circuit using standard electrical symbols.
(ii) State one advantage of connecting the lamps in parallel rather than in series.
▶️Answer/Explanation
(i) The circuit diagram should include:
- Two cells connected in series.
- Two lamps connected in parallel.
- Two switches, each controlling one lamp.
(ii) One advantage of connecting the lamps in parallel is that if one lamp fails, the other lamp will still light.
Detailed Solution:
(i) In a parallel circuit, each component has its own separate path for current flow. The circuit diagram should show two cells in series (connected end-to-end) and two lamps in parallel (each connected across the same two points in the circuit). Each lamp should have its own switch to control it independently.
(ii) In a parallel circuit, the failure of one component does not affect the operation of the other components. This is because each component has its own independent path for current flow. In contrast, in a series circuit, if one component fails, the entire circuit is broken, and no current flows.
Question(b)
Fig. 3.1 shows a filament lamp.
(i) When the lamp is switched on, thermal energy is transferred from the filament through the metal base. Name the process that transfers the thermal energy.
(ii) Suggest one part of the electromagnetic spectrum emitted by the lamp.
▶️Answer/Explanation
(i) The process that transfers thermal energy is conduction.
(ii) One part of the electromagnetic spectrum emitted by the lamp is visible light or infrared radiation.
Detailed Solution:
(i) Conduction is the process by which thermal energy is transferred through a material (e.g., the metal base of the lamp) from a region of higher temperature to a region of lower temperature. In this case, thermal energy is transferred from the hot filament to the metal base.
(ii) A filament lamp emits electromagnetic radiation, including visible light (which allows us to see) and infrared radiation (which we feel as heat).
Question(c)
Fig. 3.2 shows a ray of light from the lamp passing through a rectangular glass block.
(i) On Fig. 3.2, label the angle of incidence with the letter i and the angle of refraction with the letter r.
(ii) Explain why the ray of light changes direction as it is refracted through the glass block.
▶️Answer/Explanation
(i) The angle of incidence (i) is the angle between the incident ray and the normal. The angle of refraction (r) is the angle between the refracted ray and the normal.
(ii) The ray of light changes direction because light travels at different speeds in different media. When light enters the glass block, it slows down, causing it to bend towards the normal.
Detailed Solution:
(i) The angle of incidence (i) is measured between the incident ray and the normal (a line perpendicular to the surface of the glass block). The angle of refraction (r) is measured between the refracted ray and the normal.
(ii) Refraction occurs because light changes speed when it passes from one medium (e.g., air) to another (e.g., glass). When light enters a denser medium (like glass), it slows down and bends towards the normal. This change in speed and direction is described by Snell’s Law.
Question (a)(i)
Fig. 6.1 shows an electric heater containing two heating elements.
The two heating elements are connected in series. Each heating element has a resistance of 8 Ω.
Calculate the combined resistance of the two heating elements.
▶️Answer/Explanation
Answer: 16 Ω
Explanation: When resistors are connected in series, their resistances add up. The formula for the total resistance in a series circuit is: \[ R_{\text{total}} = R_1 + R_2 \] Given: \[ R_1 = 8 \, \Omega, \quad R_2 = 8 \, \Omega \] Substituting the values: \[ R_{\text{total}} = 8 + 8 = 16 \, \Omega \] Therefore, the combined resistance is 16 Ω.
Question(a)(ii)
A different heater has the two heating elements connected in parallel.
State which value could be the combined resistance of the two heating elements connected in parallel.
Explain your answer.
▶️Answer/Explanation
Answer: 4 Ω
Explanation: When resistors are connected in parallel, the total resistance is less than the smallest individual resistance. The formula for the total resistance in a parallel circuit is: \[ \frac{1}{R_{\text{total}}} = \frac{1}{R_1} + \frac{1}{R_2} \] Given: \[ R_1 = 8 \, \Omega, \quad R_2 = 8 \, \Omega \] Substituting the values: \[ \frac{1}{R_{\text{total}}} = \frac{1}{8} + \frac{1}{8} = \frac{2}{8} = \frac{1}{4} \] Therefore: \[ R_{\text{total}} = 4 \, \Omega \] The combined resistance in parallel is 4 Ω, which is less than either of the individual resistances.
Question(a)(iii)
Complete the circuit diagram for the two heating elements (resistors) connected in parallel to an a.c. power supply.
The circuit should contain one switch to operate both heating elements.
▶️Answer/Explanation
Answer: The circuit diagram should show:
- Two resistors (heating elements) connected in parallel.
- A switch connected in series with the power supply to control both heating elements.
Explanation: In a parallel circuit, the resistors are connected side by side, and the same voltage is applied across each resistor. The switch is placed in the main line to control the flow of current to both resistors simultaneously.
Question(b)(i)
Fig. 6.2 shows the heater on a wall in a room.
When the heater is switched on, the air around the heater is warmed.
On Fig. 6.2, draw four arrows to show how the warm air circulates around the room.
▶️Answer/Explanation
Answer: The arrows should show:
- Two arrows pointing upwards near the heater (warm air rising).
- Two arrows pointing downwards away from the heater (cool air sinking).
Explanation: Warm air rises because it is less dense than cool air. As the warm air rises, it creates a convection current where cool air moves in to replace it. This results in a circular flow of air around the room.
Question(b)(ii)
Name the process which circulates the warm air.
▶️Answer/Explanation
Answer: Convection
Explanation: Convection is the process by which heat is transferred through the movement of fluids (liquids or gases). In this case, the warm air rises, and cool air sinks, creating a convection current that circulates the air around the room.
Question(c)
A man walks on the floor in the room.
As he walks, he gains a negative charge.
Describe how the man gains this charge.
Use ideas about charged particles in your answer.
▶️Answer/Explanation
Answer: The man gains a negative charge due to the transfer of electrons from the floor to his body through friction.
Explanation: When the man walks on the floor, friction between his shoes and the floor causes electrons to be transferred from the floor to his body. Electrons are negatively charged particles, so the man gains a negative charge as he accumulates these electrons. This process is known as charging by friction.
Question
(a) The total current supplied to a television when in use is 3A.
(i) The fuse in the electrical supply to the television is replaced.
Several fuse ratings are available.
1A 3A 5A 13A 30A
State which fuse should be used.
Explain your answer.
fuse …………. A
explanation …………………………………………………………………………………………………………
▶️Answer/Explanation
Answer:
Fuse: 5A
smallest rating above working current ;
(ii) The electrical supply to the television is 120 V.
Calculate the total resistance of the television.
resistance = ………………………………………………Ω
▶️Answer/Explanation
Answer:
Resistance = Voltage / Current = 120V / 3A = 40 Ω
(b) The television is connected to a power socket which also supplies electricity to a kettle and an electric heater. The power socket is next to a kitchen sink.
Fig. 6.1 shows the power socket.
State and explain one reason why this arrangement is not safe.
▶️Answer/Explanation
Answer:
insulation broken or missing ;
fire hazard / overheating ;
or
socket overloaded ;
fire hazard / overheating ;
or
socket too close to water ;
danger of electrocution ;
(c) Television signals are carried by radio waves.
(i) On Fig. 6.2 write radio waves in the correct place in the incomplete electromagnetic spectrum.
▶️Answer/Explanation
Answer:
radio waves in right hand box ;
(ii) Fig. 6.3 represents an electromagnetic wave.
On Fig. 6.3 mark and label one wavelength. (Sub-topic – P3.1)
▶️Answer/Explanation
Answer:
peak to peak / trough to trough / equivalent ;
(d) Fig. 6.4 shows a ray of light from the television reflecting at a plane mirror.
(i) Identify the line labelled X.
▶️Answer/Explanation
Answer:
Normal
(ii) Label the angle of reflection with the letter r .
▶️Answer/Explanation
Answer:
between ray and normal ;
(iii) The angle of reflection is \( 30^\circ \).
State the angle of incidence.
angle = ………………………………………………. °
▶️Answer/Explanation
Answer:
Angle of incidence = 30°
Question
(a) A car has two identical headlamps. The lamps are connected in parallel across a 12V battery. A single switch is used to turn on both lamps.
(i) Draw a circuit diagram for this circuit using standard electrical symbols.
▶️Answer/Explanation
The circuit diagram should show:
- A 12V battery as the power source.
- Two lamps connected in parallel.
- A single switch controlling both lamps.
(ii) The resistance of each lamp is 3.0Ω. Calculate the current in each lamp when lit.
▶️Answer/Explanation
Using Ohm’s Law, \( V = IR \), the current \( I \) in each lamp is: \[ I = \frac{V}{R} = \frac{12V}{3.0\Omega} = 4A \] So, the current in each lamp is 4A.
(iii) State one reason why the lamps are connected in parallel and not in series.
▶️Answer/Explanation
The lamps are connected in parallel so that if one lamp fails, the other will still light up. In a series connection, if one lamp fails, the circuit is broken, and both lamps will turn off.
(b) A lamp consists of a glass bulb, which contains a thin metal filament attached to a metal base. The glass bulb is filled with nitrogen gas. When electricity passes through the lamp, the filament is at a very high temperature.
Fig 6.1 shows a lamp
Thermal energy is transferred from the hot filament through the nitrogen gas and through the glass bulb.
(i) State the method by which thermal energy is transferred by the nitrogen gas to the glass bulb.
▶️Answer/Explanation
The thermal energy is transferred by convection. The heated nitrogen gas rises and transfers heat to the glass bulb.
(ii) State the method by which thermal energy is transferred through the glass bulb.
▶️Answer/Explanation
The thermal energy is transferred through the glass bulb by conduction. Heat is conducted through the glass material.
(c) On a journey, a car becomes electrostatically charged. Describe what happens to cause the car to become charged.
▶️Answer/Explanation
The car becomes electrostatically charged due to friction between the car’s surface and the air or road. This friction causes electrons to be transferred, resulting in an imbalance of charges, making the car charged.
(d) Fig. 6.2 shows how damage to a steel door of the car has been repaired with a plastic filler. The filler has been painted over and cannot be seen.
Suggest how the owner of the car uses a magnet to detect the repair to the bodywork.
▶️Answer/Explanation
The owner can use a magnet to detect the repair because the steel door is magnetic, while the plastic filler is not. If the magnet does not stick to a certain area, it indicates the presence of the non-magnetic plastic filler, revealing the repair.