The quantity of resistance in an electric circuit determines the amount of current flowing in the circuit for any given voltage applied to the circuit, according to Ohm's law.
Ohms Law states that the current flowing through a resistor is proportional to the potential difference across the resistor, providing the temperature remains constant.
Resistance is measured in Ohms
The ratio of Potential difference
Current
Resistance = Voltage / Current
I know that a 2 ohm resistor has 32 coils and is (cotton covered steel wire). The unknown resistor is made out of Nichrome and has 14 coils.
Prediction
I predict that the unknown resistor will have an approximate value of 1 ohm.
Apparatus
The apparatus used for this experiment was: -
· Nickel-chromium wire
· Power pack
· Voltmeter
· Ammeter
· Wires
· Crocodile clips
Method
Check that ammeter and voltmeter are both zeroed
Start with a simple circuit.
The battery pack
The Unknown Resistor
The Variable resistor
The Ammeter which must be placed in series
The Voltmeter must be place in parallel with the resistor
Checking all components work
3.
Fill a 250ml beaker with 150ml of tap water, which the unknown resistor is then placed in. Also put a thermometer in the beaker take make sure the temperature is kept a constant as possible.
4.
Take accurate readings of the current in Amps by changing the variable resistor. Before taking the readings record the temperature.
5.
Do this when the ammeter is at 0.3, 0.5, 0.7, 1.1,1.3,1.5,1.7 amps.
(Work this out by working out the maximum amp reading and the minimum reading then divide in to equal amounts depending on how many different readings you want to take.) Take the reading of the potential difference (volts) at the amp reading stated above.
6.
I at any point the temperature increases by 2/3 oC change the water.
7. Repeat steps 3-6 a further twice.
Results Table
Analysis/Conclusion
Referring to graph A which shows that as the current increases so does voltage, which my conclusion agrees with my prediction.
E.g. when the Ammeter reads 0.3 the Voltage reads to and when the Ammeter reads 1.7 the voltage is 10.
Looking at Graph A you can see that there is a good positive correlation between Current and Potential Difference.
On my graph the line of best-fit shows that the Potential Difference is proportional to current. All point are relatively close to the Line Of best Fit.
Evaluation
I think that my results were quite accurate, as there weren’t any anomalous points. If I were to repeat the experiment I think I could improve my results even more by:
- I would take a much wider range of readings.
- I would take more readings so that a more accurate average can be taken.
