Practical: I-V graphs
Cards (11)
- I-V characteristics (I-V Graphs):GRAPHS that show how the CURRENT (I) through a component changes with the POTENTIAL DIFFERENCE (V) applied to it.
- TYPES OF I-V CHARACTERISTICS:
- LINEAR COMPONENTS
- NON-LINEAR COMPONENTS
- LINEAR COMPONENTs:Like a fixed resistor, show a STRAIGHT LINE on the graph, indicating that current & potential difference are DIRECTLY PROPORTIONAL.
- NON-LINEAR COMPONENTS:Like a filament lamp or a diode, show a CURVED LINE, meaning the relationship between current & potential difference is NOT proportional.
- Build TEST CIRCUIT with VARIABLE resistor to control current
- AMMETER in series & VOLTMETER in parallel
- The COMPONENT being tested
- Change the variable resistor to alter the CURRENT flowing through & P.D across the component
- Record READINGS from both the meters as you adjust the variable resistor
- Take multiple readings to ensure accuracy & 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
- 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 & very little in the opposite direction
- Potential difference across R decreased
- Current in R decreased
- Resistance is constant, because it's a straight line through the origin.
- measure the current in R using the ammeter
- measure the p.d. across R using the voltmeter
- vary the resistance of the variable resistor
- record a range of values of current & p.d.
- ensure current is low to avoid temperature increase
- switch circuit off between readings
- reverse connection of R to power supply repeat measurements of I & V in negative direction
- plot a graph of current against p.d.