Summary Notes - Topic 2 Electricity - Edexcel Physics IGCSE

What is current and how is it measured?

Current (I) is the rate of flow of charge and is measured in amperes (A). It is given by I=Q/t, where Q is charge in coulombs (C) and t is time in seconds (s).

What is potential difference and how is it calculated?

Potential difference (V) is the work done per unit charge in moving between two points in a circuit, measured in volts (V). It is calculated using V=E/Q.

Explain the relationship between potential difference, current, and resistance.

The relationship is described by Ohm's Law: V = IR, where V is potential difference, I is current, and R is resistance.

What is resistance and how is it defined?

Resistance (R) is measured in ohms (Ω) and is defined as the potential difference across a component divided by the current through it: R=V/I.

Differentiate between ohmic and non-ohmic conductors.

Ohmic conductors have constant resistance, where current is directly proportional to voltage. Non-ohmic conductors, like filament lamps, have resistance that changes with voltage and current.

Describe the total resistance in a series circuit.

In a series circuit, the total resistance (RT) is the sum of the resistances of each component: RT = R1 + R2 + ...

What happens to current in a parallel circuit?

In a parallel circuit, the current is shared between each branch, and the potential difference is the same across every branch.

What is a fuse and its purpose in a circuit?

A fuse is a thin piece of wire that melts if the current exceeds a certain limit, protecting the circuit from excessive current.

How does double insulation work as a safety measure?

Double insulation prevents electric shock by enclosing electrical components in plastic casings or ensuring the earth wire cannot touch the metal casing.

What is the difference between alternating current (AC) and direct current (DC)?

AC continuously changes direction, while DC flows in one direction. Mains electricity is AC, while battery supplies are DC.

What happens to charges when two insulators are rubbed together?

Electrons move from one insulator to the other, resulting in one becoming positively charged (loses electrons) and the other negatively charged (gains electrons).

Explain the phenomenon of lightning in terms of electrostatics.

Lightning occurs when electrostatic charge builds up on clouds due to friction, and when this charge discharges, it creates a lightning bolt.

What is earthing in relation to static electricity?

Earthing offers a path for excess static charge to flow into the earth, reducing the risk of electric shock and fire hazards.

How are inkjet printers and photocopiers examples of electrostatic charge applications?

Inkjet printers use charged droplets of ink that are attracted to oppositely charged plates, while photocopiers transfer toner to paper using differences in charge on a plate.