IGCSE Physics 0625 · Topic 4.2.1

IGCSE Physics Electric Charge Questions and Worked Solutions

50 topic-wise practice questions on Electric Charge (Unit 4: Electricity and Magnetism), written to the Cambridge IGCSE Physics 0625 syllabus for 2026–2028, each with a step-by-step worked solution.

50 questions23 Core17 Extended10 Challenge117 marksTextbook §4.2 · pp. 184–208

Questions tagged Core are for all candidates (Papers 1 & 3). Questions tagged Extended are Supplement content (Papers 2 & 4). Questions 41–50 are harder Challenge questions. Try each question first, then tap Show solution to check your working.

Topic guide: Electric Charge

There are two kinds of charge, positive and negative. Rubbing insulators transfers electrons, leaving one object negative and the other positive. Conductors let charge move; insulators do not.

Key formulas

Q in coulombs (C)	unit of charge	Extended
number of electrons = Q ÷ e	e = 1.6 × 10⁻¹⁹ C (useful, not on the syllabus list)	Extended

Prerequisite knowledge

Atomic structure: electrons are negative (5.1.1)

Exam tips & common mistakes

Positive charge is NEVER transferred in rubbing — only electrons move
Field lines point away from + and towards −
Electrostatic attraction of uncharged objects is due to induced charge

Key facts from the syllabus (4.2.1)

Like charges repel; unlike charges attract
Charging by friction transfers only negative charge (electrons)
Gaining electrons → negative; losing electrons → positive
Detect charge with a gold-leaf electroscope or by attracting small pieces of paper
Distinguish conductors and insulators with a simple circuit and a lamp/meter
Metals conduct because they have free electrons; insulators have no free electrons
Extended an electric field is a region where a charge experiences a force; its direction is the force on a positive charge
Extended field patterns — radial around a point charge and a charged sphere; uniform between parallel plates

Textbook: §4.2 Electrical quantities, pp. 184–208

Core[1 mark]

State the two types of electric charge.

Show solutionHide solution

Method: Positive and negative.

Positive and negative

Core[2 marks]

State the rules for forces between charges.

Show solutionHide solution

Method: Like repel, unlike attract.

Like charges repel; unlike (opposite) charges attract

Core[3 marks]

Describe a simple experiment to show charging by friction.

Show solutionHide solution

Method: Rub rod with cloth, pick up paper.

Rub a polythene rod with a dry cloth; the charged rod attracts small pieces of paper (or deflects a stream of water)

Core[2 marks]

A polythene rod becomes negatively charged when rubbed with a cloth. Explain this.

Show solutionHide solution

Method: Electrons move.

Electrons move from the cloth to the rod, giving the rod extra electrons

Core[2 marks]

An acetate rod becomes positively charged when rubbed with a cloth. Explain this.

Show solutionHide solution

Method: Electrons lost.

Electrons move from the rod to the cloth, so the rod has fewer electrons than protons

Core[1 mark]

State which particles move when solids are charged by friction.

Show solutionHide solution

Method: Electrons.

Electrons (negative charge only)

Core[2 marks]

Describe how to detect whether an object is charged.

Show solutionHide solution

Method: Gold-leaf electroscope or attraction.

Bring it near small pieces of paper or a gold-leaf electroscope; if paper is attracted or the leaf rises, it is charged

Core[3 marks]

Describe an experiment to distinguish between electrical conductors and insulators.

Show solutionHide solution

Method: Circuit with gap and lamp.

Connect a cell, lamp and two leads with a gap; place each material across the gap; if the lamp lights it is a conductor

Core[2 marks]

Use the electron model to explain why metals are good conductors.

Show solutionHide solution

Method: Free electrons.

Metals have free (delocalised) electrons that can move through the material

Core[2 marks]

Use the electron model to explain why plastics are insulators.

Show solutionHide solution

Method: No free electrons.

Their electrons are held tightly and are not free to move

Core[2 marks]

Give two examples of conductors and two of insulators.

Show solutionHide solution

Method: Metals/graphite vs plastic/rubber.

Conductors: copper, aluminium (graphite); insulators: plastic, rubber, glass, wood

Core[2 marks]

Two charged balloons repel. One has a negative charge. State the charge on the other and explain.

Show solutionHide solution

Method: Like charges repel.

Negative, because like charges repel

Core[2 marks]

A balloon rubbed on hair sticks to a wall. Explain why.

Show solutionHide solution

Method: Charging by friction.

The balloon gains electrons and becomes negatively charged; it attracts the wall by inducing opposite charge on its surface

Core[2 marks]

Two rods are rubbed and then repel each other. State what this tells you about their charges.

Show solutionHide solution

Method: Like charges.

They have the same type of charge

Core[2 marks]

A rod with a negative charge attracts another rod. State the possible charges on the second rod.

Show solutionHide solution

Method: Opposite or neutral.

Positive or uncharged

Core[2 marks]

State why metals cannot easily be charged by rubbing while held in the hand.

Show solutionHide solution

Method: Conduct charge away.

Charge flows through the metal and the person to earth

Core[2 marks]

State which particle is transferred when a cloth and a rod are rubbed together.

Show solutionHide solution

Method: Electrons.

Electrons

Core[2 marks]

A polythene rod gains 4 × 10¹⁰ electrons. State the sign of its charge and of the cloth's charge.

Show solutionHide solution

Method: Rod negative.

Rod: negative; cloth: positive

Core[2 marks]

Explain why aircraft are earthed before refuelling.

Show solutionHide solution

Method: Static sparks.

Charge built up by friction could cause a spark and ignite the fuel

Core[3 marks]

Describe how a gold-leaf electroscope shows that an object is charged.

Show solutionHide solution

Method: Leaf rises.

When a charged object touches or comes near the cap, charge spreads to the stem and leaf; like charges repel and the leaf rises

Core[2 marks]

State two examples of electrical insulators used in everyday wiring.

Show solutionHide solution

Method: Plastic, rubber.

PVC (plastic) insulation and rubber

Core[2 marks]

State whether graphite is a conductor or insulator.

Show solutionHide solution

Method: Conductor.

Conductor

Core[2 marks]

Explain why electricians wear rubber gloves.

Show solutionHide solution

Method: Insulator.

Rubber is an insulator, preventing current flowing through them

Extended[1 mark]

State the unit of charge.

Show solutionHide solution

Method: Coulomb.

coulomb (C)

Extended[1 mark]

Define an electric field.

Show solutionHide solution

Method: Region of force on a charge.

A region in which an electric charge experiences a force

Extended[1 mark]

State the direction of an electric field at a point.

Show solutionHide solution

Method: Force on positive charge.

The direction of the force on a positive charge at that point

Extended[2 marks]

Describe the electric field around an isolated positive point charge.

Show solutionHide solution

Method: Radial outwards.

Radial lines pointing outwards from the charge

Extended[2 marks]

Describe the electric field around a negatively charged conducting sphere.

Show solutionHide solution

Method: Radial inwards.

Radial lines pointing inwards towards the sphere, at 90° to its surface

Extended[2 marks]

Describe the electric field between two oppositely charged parallel plates.

Show solutionHide solution

Method: Uniform.

Parallel, evenly spaced lines from the positive plate to the negative plate (uniform field)

Extended[2 marks]

A small negative charge is placed between parallel plates. State the direction of the force on it.

Show solutionHide solution

Method: Opposite to the field.

Towards the positive plate (opposite to the field direction)

Extended[2 marks]

A charged rod attracts an uncharged piece of paper. Explain why.

Show solutionHide solution

Method: Induced charge separation.

The rod induces opposite charge on the near side of the paper, which is attracted more strongly than the like charge on the far side is repelled

Extended[2 marks]

A charge of −3.2 × 10⁻¹⁹ C is on a dust particle. Calculate the number of extra electrons (e = 1.6 × 10⁻¹⁹ C).

Show solutionHide solution

Method: n = Q/e.

2 electrons

Extended[2 marks]

Describe the direction of the electric field between a positive plate (top) and a negative plate (bottom).

Show solutionHide solution

Method: Positive to negative.

Downwards, from the positive to the negative plate

Extended[2 marks]

An electron is placed between parallel plates. State which plate it moves towards and why.

Show solutionHide solution

Method: Opposite force.

Towards the positive plate, because it is negatively charged

Extended[2 marks]

Describe the electric field pattern around a negative point charge.

Show solutionHide solution

Method: Radial inward.

Radial lines pointing inwards towards the charge

Extended[2 marks]

Describe how the strength of the field around a point charge changes with distance.

Show solutionHide solution

Method: Weaker further away.

It becomes weaker further from the charge (lines spread out)

Extended[2 marks]

Explain the difference between a magnetic field and an electric field in terms of what experiences the force.

Show solutionHide solution

Method: Pole vs charge.

A magnetic field exerts a force on magnetic poles/moving charges; an electric field exerts a force on charges

Extended[3 marks]

Describe and sketch the electric field around a positively charged metal sphere.

Show solutionHide solution

Method: Radial outward, perpendicular to surface.

Radial lines pointing outwards from the surface, at right angles to it, like a point charge at the centre

Extended[2 marks]

State the unit of electric charge and how it relates to current and time.

Show solutionHide solution

Method: C = A s.

coulomb; 1 C = 1 A × 1 s

Extended[2 marks]

Explain why a dust particle carrying positive charge moves towards a negatively charged plate.

Show solutionHide solution

Method: Attraction in field.

It experiences a force in the electric field towards the negative plate (opposite charges attract)

Challenge questions

Harder, multi-step questions at the top end of the exam. Attempt these once you are confident with the questions above.

ChallengeCore[4 marks]

Describe how to charge a polythene rod by friction and test whether it is positive or negative using a charged acetate rod.

Show solutionHide solution

Method: Repulsion test.

Rub with a dry cloth; bring it near a suspended charged acetate rod (positive); if they attract, the polythene is negative

ChallengeCore[4 marks]

Explain why rubbing a balloon makes it stick to a wall, using electrons and induced charge.

Show solutionHide solution

Method: Transfer and induction.

Electrons move onto the balloon; near the wall, the balloon repels electrons in the wall surface, leaving it positive; the opposite charges attract

ChallengeCore[3 marks]

Explain why a conductor cannot be charged by friction if held in the hand, but can if mounted on an insulating stand.

Show solutionHide solution

Method: Charge flows to earth.

Charge flows away through the conductor and the person; insulating the conductor traps the charge

ChallengeCore[4 marks]

Use the electron model to explain why metals are conductors and plastics are insulators, giving one example of each.

Show solutionHide solution

Method: Free electrons.

Metals (e.g. copper) have free electrons that move through the material; plastics (e.g. PVC) have electrons bound to atoms that cannot move

ChallengeExtended[4 marks]

A charged sphere carries −4.8 × 10⁻⁹ C. Calculate the number of excess electrons (e = 1.6 × 10⁻¹⁹ C).

Show solutionHide solution

Method: n = Q/e.

n = 3.0 × 10¹⁰

ChallengeExtended[4 marks]

Sketch and describe the electric field between two oppositely charged parallel plates and around a single positive point charge. Explain the difference in uniformity.

Show solutionHide solution

Method: Uniform vs radial.

Between plates: parallel, equally spaced lines from + to − (uniform); around a point charge: radial lines outward that spread apart (weakening with distance)

ChallengeExtended[4 marks]

An oil drop with a negative charge is held stationary between horizontal plates. State the direction of the electric field and the plate that is positive. Explain.

Show solutionHide solution

Method: Upward force needed.

The electric force must be upwards; for a negative charge the field points downwards, so the top plate is positive

ChallengeExtended[4 marks]

Explain how an electrostatic paint spray uses charge to coat a car body evenly.

Show solutionHide solution

Method: Repulsion and attraction.

Paint droplets are given the same charge so they repel and spread; the car is given the opposite charge (or earthed) so droplets are attracted, coating even hidden surfaces

ChallengeExtended[3 marks]

Explain why an alpha particle and an electron moving through the same electric field are deflected in opposite directions.

Show solutionHide solution

Method: Opposite charges.

They carry opposite charges, so the forces on them are opposite

ChallengeExtended[4 marks]

Explain how a gold-leaf electroscope can be used to tell whether an object is positively or negatively charged.

Show solutionHide solution

Method: Pre-charge.

Charge the electroscope with a known (e.g. negative) charge; bring the object near: if the leaf rises further it has the same charge; if the leaf falls it has the opposite charge

All IGCSE Physics topics ← 4.1 Simple Phenomena of Magnetism 4.2.2 Electric Current →

Book a free trial class

Tell us a little about your requirement.