Cambridge IGCSE Physics Notes 4.2: Electrical Quantities
Cambridge IGCSE Physics notes on charge, current, electromotive force, potential difference, resistance, electrical energy, and power.
Q: What does Cambridge IGCSE Physics Notes 4.2: Electrical Quantities cover?
A: It follows official Cambridge Physics section 4.2 for syllabuses 0625 and 0972, with Core ideas separated from Supplement depth.
Electrical quantities describe how charge moves and how energy is transferred: current is charge flow rate, voltage is energy per charge, and resistance links voltage to current.
The ideas that organise this section
- Conventional current direction is opposite to electron flow in metals.
- Electromotive force is energy supplied per charge; potential difference is energy transferred per charge in a component.
- Resistance depends on the component and conditions, so not every current-voltage graph is linear.
Core route
Core candidates should be ready to describe, calculate, interpret, and apply the following:
- Calculate charge, current, voltage, resistance, electrical energy, and power.
- Describe current in metals and the effect of changing resistance or voltage.
- Interpret simple current-voltage data and household energy use.
Supplement route
Extended candidates study all Core content and add the following depth:
- Distinguish electromotive force from potential difference through energy transfer.
- Explain non-ohmic behaviour through temperature or component response.
- Apply electrical relationships across unfamiliar devices and data sets.
Formula route
- Relationship: current = charge / time.
- Relationship: voltage = energy transferred / charge.
- Relationship: resistance = voltage / current.
- Relationship: electrical power = current x voltage.
- Relationship: electrical energy = power x time.
Write the relationship before substituting. Convert units first, keep extra figures during working, and round only the final answer to sensible precision.
Build a connected model
In Electrical Quantities, a strong answer connects the named quantity or model to observable evidence. Begin by defining the physical quantity in words or with its relationship. Identify which values are scalars and which require a direction. Represent the situation with a labelled diagram, graph, field pattern, ray or circuit when that makes the relationship visible. The representation is part of the reasoning: its labels, arrows and scale should agree with the written explanation.
