Electricity and Circuits

These flashcards cover key concepts from the lecture notes on electricity and circuits, including definitions, laws, characteristics, and important equations.

Electric Current

The flow of electric charge around a circuit, measured in amperes (A).

Potential Difference

The energy transferred per unit charge between two points in a circuit, measured in volts (V).

Resistance

Opposition to the flow of current, measured in ohms (Ω).

Ohm's Law

Current is directly proportional to potential difference if temperature is constant; V = I × R.

Series Circuits

Potential difference is shared; current is the same everywhere.

Parallel Circuits

Potential difference is the same across each branch; current is shared between branches.

Total Resistance in Series

Total resistance increases when adding resistors in series.

Total Resistance in Parallel

Total resistance decreases when adding resistors in parallel.

IV Characteristics

Three components with different I–V characteristics: Resistor, filament lamp, diode.

Filament Lamp I-V Characteristic

As current increases, temperature and resistance increase, causing the graph to curve.

Diode I-V Characteristic

Current only flows in one direction; resistance is very high in the reverse direction.

Power Equations

Three equations linking power with current, voltage, and resistance: P = V × I, P = I² × R, P = V² ÷ R.

Energy Transfer Equation

E = Q × V links energy, charge, and potential difference.

Charge Flow Equation

Q = I × t links charge, current, and time.

Domestic Electricity

Frequency = 50 Hz, Potential difference = 230 V.

Cables and Plugs

Live = brown (carries current), Neutral = blue (completes circuit), Earth = green/yellow (safety).

Safety Devices

A fuse or circuit breaker cuts off the circuit if the current is too high, preventing overheating.

National Grid

Transfers electrical energy from power stations to consumers using transformers and cables.

High Voltage Transmission

Electricity is transmitted at high voltage and low current to reduce energy losses due to heating of cables.

Efficiency of Transformers

Step-up transformers increase voltage to reduce current (less heat loss), step-down transformers lower voltage for safe domestic use.