- Every component of an elecrtric circuit has its own agreed symbol
- A circuit diagram shows how components are connected together
- A battery consists of 2 or more cells connected together
Resistance (ohms) = potential current (volts) / current (amps)
The current through a resistor at constant temperature is directly proportional to the potential difference across the resistor.
We say a wire is a ohmic conductor because it resistance is constant.
Current-Potential Difference Graphs
Filament Lamp: resistance increases with increase of filament temperature
Diode: 'forward' resistance is low. 'reverse' resistance is high.
Thermistor: resistance decreases if its temperature increases.
LDR: resistance decreases if the light intensity on it increases.
The same current passes through components in series with each other.
The total potential difference of the voltage supply in a series circuit is shared between the components.
The total potential difference of cells in series is the sum of the potential difference of each cell.
The total resistance of components in series is equal to the sum of their separate resistances
The total curent through the whole circuit is the sum of the currents through the separate components.
For components in parallel, the potential difference across each component is the same.
Current (amps) = potential difference (volts) / resistance (ohms)
The bigger the resistance of a compound, the smaller its current is.