Electrical Circuits
Charge and current💡
Circuit diagrams are used to show electrical circuits. When there is a complete closed circuit, and electrical current will flow.
- Electric current is a flow of charge. In copper wires, the charge is due to negatively charged electrons.
- Electric current is measured in amperes (A), using an ammeter connected in series.
- The electrons in the circuit are attracted to the positive terminal of the battery, but conventional current flows from positive to negative.
A circuit diagram showing an ammeter connected in a series.
Types of Circuits: You will have to know about the series and parallel circuits in I/GCSE Physics
- In series circuits, components are connected end to end in a single loop. The current is the same all the way round the series circuit. An ammeter placed at two points will show the same reading.
- In parallel circuits, the components are connected across each other. The current will split at two junctions.
- The unit of electric charge is called the coulomb (C). An electron carries a tiny amount of charge - only -1.6 X 10 ^-19 C (minus 1.6 times 10 to the power of -19 coulombs).
Electrical current (A) = electrical charge (C) / time (s)
Voltage⚡️
The cell or battery in a circuit gives energy to the electrons so that they can transfer energy to the components in the circuit.
- The chemical energy in the cell is converted to electrical energy of the electrons.
A voltmeter measures the amount of energy transferred in a component. It is connected in parallel across the component.
- The voltage, or potential difference, is measure in volts.
In series circuits, the voltage across individual components adds up to the voltage across the power supply:
V = V1 = V2
In parallel circuits, the voltage across each component is the same as the voltage across the power supply:
V = V1 = V2
Potential difference is the amount of energy per unit charge. A p.d. of 1 volt is 1 joule of energy per coulomb of charge.
Potential difference (volt) = energy (joule) / charge (coulomb)
Drafted by Catrina (Physics)