What does the current through an electrical circuit depend on?
The size of the current in a circuit depends on how hard the supply tries to push charge through the circuit and how hard the circuit resists having charge pushed through it.
You must be able to interpret and draw circuit diagrams using standard symbols.
The following standard symbols should be known:
Current Voltage Graphs
Current-potential difference graphs are used to show how the current through a component varies with the potential difference across it.
Current, Voltage and Resistance
The current through a resistor (at a constant temperature) is directly proportional to the potential difference across the resistor.
Potential difference, current and resistance are related by the equation:
potential difference = current × resistance
(volts, V) (amps, A) (ohms, Ω)
The current through a component depends on its resistance. The greater the resistance the smaller the current (if the voltage is the same).
The resistance of a component can be found by measuring the current through, and potential difference across, the component.
More Components
The resistance of a filament lamp increases as the temperature of the filament increases.
The current through a diode flows in one direction only. The diode has a very high resistance in the reverse direction.
The resistance of a light-dependent resistor (LDR) decreases as light intensity increases.
The resistance of a thermistor decreases as the temperature increases
Series and Parallel Circuits
The potential difference provided by cells connected in series is the sum of the potential difference of each cell (depending on the direction in which they are connected).
For components connected in series:
For components connected in parallel: