CIE iGCSE Co-Ordinated Science P4.5.2 The a.c. generator Exam Style Questions Paper 3
Question
State what has been added to or removed from the car for it to become charged.
State the type of energy stored in the fuel.
Explain why this is.
Complete the sentences to describe how a solar cell can provide energy.
Light energy from the …………….. is absorbed by the solar cell.
The solar cell changes the light energy to ………………. energy.
The turning effect of the motor can be increased by increasing the number of turns on the coil in the motor.
State one other way to increase the turning effect of the d.c. motor.
The lamps are connected in parallel.
Complete the circuit diagram in Fig. 6.1 to show the two lamps connected in parallel, both controlled by one switch.
The battery has been drawn for you.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P1.6.1 — Energy (Parts (a)(i), (a)(iii), (a)(iv))
• Topic P4.2.1 — Electrical charge (Part (a)(ii))
• Topic P6.2.3 — Galaxies and the Universe (Part (b))
• Topic P4.5.5 — The d.c. motor (Part (c))
• Topic P4.5.1 — Electromagnetic induction (Part (d)(i))
• Topic P4.5.2 — The a.c. generator (Part (d)(ii))
• Topic P4.5.6 — The transformer (Part (d)(ii))
▶️ Answer/Explanation
(a)(i) Kinetic energy
A moving object possesses kinetic energy because of its motion.
The faster the car moves, the greater its kinetic energy.
Kinetic energy depends on both the mass and speed of the car.
(a)(ii) Electrons
Electrostatic charging occurs when electrons are transferred between surfaces.
Friction between the car and the air (or road) causes electrons to be added to or removed from the car.
This leaves the car with an overall electric charge.
(a)(iii) Chemical potential energy
Fuel stores energy in the chemical bonds of its molecules.
This is released as thermal energy during combustion in the engine.
The energy is described as chemical potential energy.
(a)(iv)
Not all of the chemical energy is converted into useful kinetic energy.
Some energy is transferred to thermal energy due to friction in moving parts.
Some energy is also transferred as sound energy, and both are lost to the surroundings.
(b) Sun; electrical
Light energy from the Sun reaches the solar cell.
The solar cell absorbs this light energy.
It then converts (transfers) the light energy into electrical energy.
(c) Increase the strength of the magnetic field, or increase the current
The turning effect (torque) on the coil depends on the magnetic field strength, current, and number of turns.
Increasing the current passing through the coil increases the force on it.
A stronger magnetic field also increases the turning effect for the same current.
(d)(i)
The circuit is drawn with the two lamps on separate parallel branches.
Both branches connect back to the same battery, so each lamp receives the full battery voltage.
A single switch is placed in the main circuit (before the branches split) so that it controls both lamps together.
(d)(ii) If one lamp fails, the other still lights up
In a parallel circuit, each lamp is connected on its own independent branch.
If one branch breaks (lamp fails), current can still flow through the other branch.
This means the remaining lamp continues to work normally.
Question
Readings are recorded on ammeters A₁ and A₂.
Describe the difference, if any, in the readings of A₁ and A₂.
Explain your answer.
An argon atom has the chemical symbol \( ^{40}_{18}\text{Ar} \).
State the composition of the nucleus of an atom of Argon.
Explain this observation.
Most-appropriate topic codes (Cambridge IGCSE Co-ordinated Sciences 0654):
• Topic P4.3.1 — Circuit diagrams and circuit components (Part (a)(i))
• Topic P4.5.2 — The a.c. generator (Part (a)(ii))
• Topic P4.5.1 — Electromagnetic induction (Part (a)(iii))
• Topic P4.4 — Electrical safety (Part (b))
• Topic P5.1 — The nucleus (Part (c))
• Topic P5.2.2 — The three types of nuclear emission (Part (d)(i))
• Topic P5.2.1 — Detection of radioactivity (Part (d)(ii))
▶️ Answer/Explanation
(a)(i) P: Variable resistor; Q: Voltmeter
P is drawn as a rectangle with a diagonal arrow, the standard symbol for a variable resistor.
Q is connected across a component in the circuit, shown as a circle labelled V — this is a voltmeter.
A voltmeter is always connected in parallel with the component it measures.
(a)(ii) Volt (V)
Electromotive force (e.m.f.) is the energy provided per unit charge by a source.
It is measured in the same unit as potential difference.
The SI unit of e.m.f. is the volt (V).
(a)(iii) Ammeter A₁ reads lower than ammeter A₂
A₂ is positioned in the main circuit, so it reads the total current supplied by the source.
A₁ is positioned in one of the parallel branches, so it reads only the current through that branch.
Since the total current splits between the two parallel branches, \(I_{A_2} > I_{A_1}\).
(b) Damaged cable / insulation damaged
The diagram shows the power cable with exposed or frayed insulation.
Damaged insulation can expose the live wire.
This creates a risk of electric shock or short circuit.
(c) 18 protons and 22 neutrons
The atomic (proton) number, 18, gives the number of protons.
The mass (nucleon) number, 40, gives the total number of protons and neutrons.
Number of neutrons = \(40 – 18 = 22\).
(d)(i) Compare count rate with and without paper shielding
Record the count rate from the detector with nothing between it and the sample.
Place a sheet of paper between the sample and the detector, then record the count rate again.
If the count rate falls significantly (or to near background level), this shows α-particles are being emitted, since paper readily absorbs α-radiation.
(d)(ii) Background radiation
Radiation is present in the environment from natural sources such as rocks, cosmic rays, and air.
This is called background radiation and is detected at all times, even without the sample.
It explains why some count is still recorded once the rock sample is removed.