PEKA - Electromotive force and Internal Resistance

Aim :

To study the relationship between the potential difference and current of the dry cells

Hypothesis:

The potential difference across the terminals of dry cells decrease when the current supplied by the cells increase .

Variables:

Manipulated: Current, I
Responding: Potential difference across the terminals, V
Constant: Dry cell used

Apparatus/Materials:

Dry cells, ammeter, voltmeter, rheostat, resistor, switch, connecting wires

Procedure:


1. A circuit as shown in the diagram above is set up.
2. The switch is started. The rheostat is adjusted until the ammeter reading shows 0.2 A. The voltmeter reading is recorded.
3. Step 2 is repeated with current values of 0.3 A, 0.4 A, and 0.5 A.
4. A graph of V against I is plotted. The slope of the graph is calculated and the V-crossing is extrapolated.

Results:
Analysis:
Internal resistance, r = slope value
Electromotive force, E = V-crossing

Conclusion:
The hypothesis is accepted, from the experiment, the potential difference across the dry cells when the current supplied increases.