Required Practical: I-V Graphs
This practical investigates the I-V CHARACTERISTICS of different components.
I-V characteristics are GRAPHS that show how the CURRENT (I) through a component changes with the POTENTIAL DIFFERENCE (V) applied to it (also know as I-V Graphs).
TYPES OF I-V CHARACTERISTICS:
- LINEAR COMPONENTS (like a fixed resistor) show a STRAIGHT LINE on the graph, indicating that current and potential difference are DIRECTLY PROPORTIONAL.
- NON-LINEAR COMPONENTS (like a filament lamp or a diode) show a CURVED LINE, meaning the relationship between current and potential difference is NOT proportional.
METHOD
- Build the TEST CIRCUIT with a VARIABLE RESISTOR to CONTROL current, an AMMETER in series to measure CURRENT, a VOLTMETER in parallel to measure POTENTIAL DIFFERENCE and the COMPONENT being tested.
- Change the variable resistor to alter the CURRENT flowing through and the POTENTIAL DIFFERENCE across the component.
- Record READINGS from both the ammeter and voltmeter as you adjust the variable resistor. Take multiple readings to ensure accuracy and calculate an average.
- SWAP the connections to the battery to reverse the current's direction. This checks the component’s behaviour in both directions.
- PLOT a graph of current against voltage to visualise the component's I-V characteristics.
GRAPH ANALYSIS:
The graph you get will be different depending on the component being tested:
- The graph for an OHMIC CONDUCTOR (like a resistor) will be a straight line.
- The graph for a FILAMENT LAMP will start to curve as the current increases due to the filament heating up.
- The graph for a DIODE will show current flow in one direction and very little in the opposite direction.