Electricity: Ohm's Law & Internal Resistance
Wiring circuits with cells, voltmeters and ammeters to determine EMF and internal resistance.
STATUS
This lab is in development.
When complete, this will be a guided, step-by-step 3D simulation of the real physics practical. For now, you can read exactly what the simulation will cover below.
What you’ll do
The guided simulation will walk you through these steps in order.
- 01Connect the cell(s), ammeter (in series), and a variable resistor in a simple circuit; connect the voltmeter in parallel across the cell terminals.
- 02Set the variable resistor to its maximum resistance; close the switch and record the voltmeter reading (terminal p.d.) and ammeter reading (current I).
- 03Decrease resistance in steps; record V and I at each setting - aim for 6–8 pairs of readings.
- 04Plot a V–I graph (V on y-axis, I on x-axis); the gradient gives the negative of internal resistance (−r) and the y-intercept gives the EMF (ε).
- 05Read off ε and r from the graph; compare with the manufacturer's stated EMF if available.
- 06State sources of uncertainty (e.g. ammeter resistance, cell warming during the experiment).