Plot current against voltage and each component signs its name in the shape of the line. A straight line, a gentle curve, a one-way valve: read the graph and you read the component.
For a metal resistor at constant temperature the current is proportional to the p.d., a straight line through the origin. A filament lamp gives a curve that flattens as it heats and its resistance rises. A diode allows current in one direction only.
A current-voltage graph shows how the current through a component varies with the p.d. across it. A straight line through the origin means the resistance is constant.
A filament lamp curves because heating raises its resistance; a diode conducts one way only.
Trace the graph for a mystery component and decide what it is from the shape.
Four quick checks. Each correct answer earns XP and lights this skill on your star map.
A fixed resistor at constant temperature gives a current-voltage graph that is...
As a filament lamp gets hotter, its resistance...
A diode allows current to flow...
A straight line through the origin on a current-voltage graph means the resistance is...
Resistor, lamp and diode each give a distinctive line.
| Component | Current-voltage graph |
|---|---|
| Fixed resistor (constant temperature) | Straight line through the origin |
| Filament lamp | Curve that flattens as it heats, resistance rises |
| Diode | Current in one direction only |
Only a fixed resistor at constant temperature gives a straight line through the origin. The filament lamp curves because heating it raises its resistance, and the diode passes current in only one direction.
Unlocks once the four checks above are done. Worth more XP, written in the style of Paper 2.
A component gives a current-voltage graph that curves and flattens as the voltage rises. It is most likely a...
A current-voltage graph shows current only for positive voltages and none for negative. The component is a...
For a metal wire kept at constant temperature, doubling the p.d. across it...
Current-voltage graphs are mapped. Keep the chain going.