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CIE iGCSE Co-Ordinated Science P4.3.2 Series and parallel circuits Exam Style Questions Paper 3

CIE iGCSE Co-Ordinated Science Paper 3 - All Chapters

Question

(a) Fig. 12.1 shows four forces, A, B, C and D, acting on a car moving along a level road.
(i) State which force, A, B, C or D, is partly caused by air resistance.
(ii) One of the forces shown on Fig. 12.1 is the weight of the car.
Explain why the definition of weight below is incorrect.
“weight is a measure of the quantity of matter in an object”
(iii) The car is moving at constant speed. Force D is 2000 N.
State the value of force B. Explain your answer.
(b) As the car slows down the sound of the engine becomes quieter and the frequency of the sound waves decreases.
(i) State what happens to the amplitude of the sound waves.
(ii) State what happens to the pitch of the sound.
(c) The car has two identical headlamps P and Q, connected in a parallel circuit.
Fig. 12.2 shows the circuit diagram.
(i) State the name of the component in the circuit that causes a current to flow in the circuit.
(ii) The current in each lamp is 4 A. State the current at point X in the circuit. Choose from the values below.
0A      2A      4A      8A
Explain your answer.
(iii) State one reason why the headlamps in the car are connected in parallel rather than in series.
(d) The driver uses a plane mirror in the car to see an image of a bus behind the car.
Describe the characteristics of the image of the bus compared with the bus.

Most-appropriate topic codes (Cambridge IGCSE Coordinated Sciences 0654):

• Topic P1.5.1 — Effects of forces (Part (a)(i), (a)(ii), (a)(iii))
• Topic P3.4 — Sound (Part (b)(i), (b)(ii))
• Topic P4.3.2 — Series and parallel circuits (Part (c)(i), (c)(ii), (c)(iii))
• Topic P3.2.1 — Reflection of light (Part (d))

▶️ Answer/Explanation

(a)(i) D
Force D opposes the motion of the car and is partly caused by air resistance (drag), which increases with speed.

(a)(ii) weight is the gravitational force on an object that has mass / definition of mass (not weight)
The statement describes mass (the quantity of matter). Weight is the gravitational force acting on an object due to its mass in a gravitational field.

(a)(iii) 2000 (N) and (constant speed so) no resultant force
At constant speed, the driving force (B) equals the resisting force (D) because there is no resultant force and no acceleration. Therefore B = D = 2000 N.

(b)(i) decreases
The amplitude of a sound wave is related to loudness. A quieter sound has a smaller amplitude.

(b)(ii) decreases
Pitch is related to frequency. A lower frequency sound has a lower pitch. The engine note becomes lower in pitch.

(c)(i) battery
The battery provides the electromotive force (voltage) that causes current to flow through the circuit.

(c)(ii) 8 (A); current in main part of circuit is greater than current in either branch
In a parallel circuit, the total current from the source equals the sum of the currents in each branch. Current at X = 4 + 4 = 8 A.

(c)(iii) full voltage across both lamps OR if one lamp fails, the other will still work
Parallel connection ensures each lamp receives the full supply voltage and operates independently. If one fails, the other continues to work.

(d) any two from: same size; same distance from mirror; laterally inverted
A plane mirror produces an image that is: same size as the object, same distance behind the mirror as the object is in front, and laterally inverted (left-right reversed). The image is also virtual and upright.

Question

Fig. 12.1 shows a refrigerator.
(a) The air inside the refrigerator is cooled by a freezing compartment.
On Fig. 12.1 draw one straight arrow to show the movement of the cooled air inside the refrigerator.
(b) Some ice is made from water in the freezing compartment.
(i) State the freezing point of water.
(ii) Complete the diagrams in Fig. 12.2 to show the arrangement of water molecules in liquid water and in solid ice.
One molecule has been drawn for you in each box.
Each box must contain at least 9 molecules.
(c) The refrigerator uses electricity to:
  • power two lamps connected in series inside the refrigerator
  • power an electric motor connected in parallel with the two lamps.
(i) Complete the circuit diagram in Fig. 12.3 for the refrigerator.
(ii) One of the lamps has a resistance of 6000 Ω and the other lamp has a resistance of 3000 Ω. Calculate the combined resistance of the two lamps connected in series.

Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):

• Topic P2.3.2 — Convection (Part (a))
• Topic P2.2.2 — Melting, boiling and evaporation (Part (b)(i))
• Topic P2.1.2 — Particle model (Part (b)(ii))
• Topic P4.3.2 — Series and parallel circuits (Part (c)(i))
• Topic P4.2.4 — Resistance (Part (c)(ii))

▶️ Answer/Explanation

(a) arrow drawn downwards from the freezing compartment

The air in contact with the freezing compartment is cooled, becomes denser, and sinks downwards. Warmer air at the bottom rises to replace it, creating a convection current. The arrow should show the cooled air moving downwards within the refrigerator.

(b)(i) 0°C

The freezing point of pure water at standard atmospheric pressure is 0°C. At this temperature, liquid water changes state to solid ice.

(b)(ii) Liquid water: at least 9 particles touching, randomly arranged; Solid ice: at least 9 particles touching, regularly arranged in a lattice structure

In liquid water, the molecules are close together (touching) but have a random arrangement as they can move past each other. In solid ice, the molecules are held in fixed positions in a regular, ordered lattice structure, with a specific arrangement (often drawn as a hexagonal pattern).

(c)(i) Circuit diagram should show:

  • Correct circuit symbols for the two lamps and the motor
  • The two lamps connected in series with each other (one after the other in the same branch)
  • The motor connected in parallel with the lamps (in a separate branch)

(c)(ii) 9000 Ω

For resistors connected in series: total resistance = R₁ + R₂ + …

Combined resistance = 6000 Ω + 3000 Ω = 9000 Ω.

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