5.1.1

# Basics of Electricity

Test yourself

## Current

Current flows around any circuit where there is a potential difference.

### Charge

• Current is the rate of flow of charge.
• Electrons are charged particles which are allowed to move in metal.
• When a potential difference is applied the electrons have the 'push' they need to move.
• The flow of electrons is current.
• Electrons flow from the negative terminal to the positive terminal of a circuit.
• The current in a circuit can be measured by connecting an ammeter in series.

### Calculation

• Current moves in the opposite direction to the flow of electrons (positive to negative).
• The equation for calculating current is:
• Current = the charge flowing ÷ the time taken
• $I=\frac{ΔQ}{Δt}$
• The units of current are Amps (A).

## Potential Difference

The potential difference is also known as the voltage.

### A 'push'

• The potential difference or voltage of a circuit is the amount of work done to move the charge around the circuit, per unit charge.
• The voltage can be thought of as a 'push' that allows the current to flow around a circuit - it supplies the power to a circuit.
• Voltage can be measured by connecting a voltmeter in parallel.

### Calculation

• Voltage is the work done per unit charge. The equation for voltage is:
• Voltage = work done ÷ the charge flowing
• $V=\frac{W}{Q}$
• The units for potential difference are Volts (V)

## Resistance

Resistance is how hard it is to get a flow of electrons through a material.

### Resistance to motion

• Current is electrons flowing around a circuit.
• If the current had to travel through a component which has resistance then some work has to be done to 'push' the electrons through it.
• There is always a voltage drop across components with resistance.

### Ohm's law

• Ohm's law relates the current, voltage and resistance. The equation for Ohm's law is:
• Voltage = current x resistance
• $V=IR$

### Calculating resistance

• Ohm's law can be rearranged to allow us to calculate resistance:
• Resistance = voltage ÷ current
• $R=\frac{V}{I}$