# Electricity and Magnetism

> CIE IGCSE Physics · CIE IGCSE Physics (0625)
> Source: https://www.owlsprep.com/study/cie-0625-u4-overview/
> Weight: 20-25% of total exam (covers MCQ, structured and extended response questions)

This unit covers fundamental magnetism, static electricity, electrical circuits, and interconnected electromagnetism effects, with real-world applications aligned to the CIE IGCSE 0625 syllabus.

**Prerequisites:** [Fundamental energy concepts from Unit 1: General Physics](https://www.owlsprep.com/study/cie-0625-u1-overview/)

## Learning objectives

- Explain core properties of magnets, static electricity, and electrical circuit components
- Solve quantitative problems involving current, resistance, power, and series/parallel circuit rules
- Describe the two-way link between electricity and magnetism, including induction, motors, generators and transformers
- Apply electrical safety principles to real-world domestic circuit contexts

## Unit at a glance

The unit is structured to build progressively from static foundational phenomena to dynamic applied systems: you will first learn core properties of magnets and static charge, before moving to quantitative circuit principles, and finally exploring the two-way relationship between electricity and magnetism for real-world technologies.

Core quantitative skills including circuit calculations and power computations are reinforced throughout the unit, with extended-only content marked clearly for higher-tier candidates.

Work through the following subtopics in order to build mastery progressively:
- [Simple Phenomena of Magnetism](https://www.owlsprep.com/study/cie-0625-u4-simple-phenomena-of-magnetism/) — Covers permanent magnets, magnetic field patterns, and magnetic induction properties.
- [Electric Charge and Electric Fields](https://www.owlsprep.com/study/cie-0625-u4-electric-charge-and-electric-fields/) — Explores static charge, charging by friction, electric field patterns, and discharge effects.
- [Electric Current, e.m.f. and Potential Difference](https://www.owlsprep.com/study/cie-0625-u4-electric-current-e-m-f/) — Defines current, electromotive force, and potential difference linked to charge and energy transfer.
- [Resistance](https://www.owlsprep.com/study/cie-0625-u4-resistance/) — Covers factors affecting resistance, Ohm’s Law, and I-V characteristics for common components.
- [Electrical Energy, Power and the kW·h](https://www.owlsprep.com/study/cie-0625-u4-electrical-energy-power-and-the/) — Calculates electrical energy and power, plus use of the kilowatt-hour for domestic energy billing.
- [Circuit Diagrams, Components and Potential Dividers](https://www.owlsprep.com/study/cie-0625-u4-circuit-diagrams-components-and-potential/) — Interprets standard circuit symbols, component functions, and potential divider operation.
- [Series and Parallel Circuits](https://www.owlsprep.com/study/cie-0625-u4-series-and-parallel-circuits/) — Applies current, voltage, and resistance rules to solve series and parallel circuit problems.
- [Electrical Safety](https://www.owlsprep.com/study/cie-0625-u4-electrical-safety/) — Covers domestic circuit safety features including fuses, circuit breakers, and earthing systems.
- [Electromagnetic Induction](https://www.owlsprep.com/study/cie-0625-u4-electromagnetic-induction/) — Explains electromagnetic induction principles and factors affecting induced current size.
- [The a.c. Generator (Extended Only)](https://www.owlsprep.com/study/cie-0625-u4-the-a-c-generator/) — Covers structure and operation of alternating current generators, for extended tier candidates only.
- [Magnetic Effect of a Current, the Motor Effect and the d.c. Motor](https://www.owlsprep.com/study/cie-0625-u4-magnetic-effect-of-a-current/) — Explores magnetic fields around current-carrying conductors, the motor effect, and d.c. motor operation.
- [The Transformer](https://www.owlsprep.com/study/cie-0625-u4-the-transformer/) — Covers transformer structure, operation, efficiency calculations, and use in power transmission systems.

## Common pitfalls

- **Wrong:** Confusing e.m.f. and potential difference as identical quantities
  - Why it fails: E.m.f. measures energy supplied to charge per unit, while p.d. measures energy transferred by charge across a component
  - Correct: Use context of energy source vs load to distinguish the two terms in calculations
- **Wrong:** Adding resistance values directly for parallel circuits as you do for series circuits
  - Why it fails: Total resistance in parallel is less than the smallest individual resistor, calculated via the reciprocal rule
  - Correct: Apply $1/R_{total} = 1/R_1 + 1/R_2 + ...$ for parallel circuits, $R_{total}=R_1+R_2+...$ for series circuits
- **Wrong:** Assuming transformers can operate on direct current (d.c.) inputs
  - Why it fails: Transformers require changing magnetic fields to induce voltage, which d.c. cannot produce
  - Correct: Only use transformers with alternating current (a.c.) supplies as specified in syllabus questions

## Cheatsheet

| Concept | Formula/Rule | Subtopic Reference |
| --- | --- | --- |
| Ohm's Law | $V = I R$ | Resistance |
| Electrical Power | $P = VI = I^2 R = V^2/R$ | Electrical Energy, Power and the kW·h |
| Series Circuit Current | $I_{total} = I_1 = I_2 = ...$ | Series and Parallel Circuits |
| Parallel Circuit Voltage | $V_{total} = V_1 = V_2 = ...$ | Series and Parallel Circuits |
| Transformer Turns Rule | $V_p/V_s = N_p/N_s$ | The Transformer |
| Charge Calculation | $Q = I t$ | Electric Current, e.m.f. and Potential Difference |
| Electrical Energy | $E = V I t = P t$ | Electrical Energy, Power and the kW·h |
| Ideal Transformer Power | $V_p I_p = V_s I_s$ | The Transformer |

## What's next

To start your study of this unit, begin with the first subtopic on Simple Phenomena of Magnetism, which introduces the foundational magnetic properties you will build on for all subsequent circuit and electromagnetism content. Once you have completed all subtopics in this unit, you will progress to Unit 5: Atomic Physics, which covers nuclear structure, radioactivity, and related applications aligned with the CIE IGCSE 0625 syllabus.

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From [OwlsPrep](https://www.owlsprep.com) — free study guides for A-Level, IB, AP and IGCSE, written against the official syllabus. Canonical page: https://www.owlsprep.com/study/cie-0625-u4-overview/