If we carefully look at the graph, and the results we can see that if the voltage divides the current in each specific wire, the number comes the same. In 1826, George Ohm had conducted several experiments with different metal wires to discover how the current through each depended on the voltage applied across its ends. Ohm’s law states, “The current flowing through a metal conductor is directly proportional to the p.d. across its ends provided the temperature and other physical conditions remain constant.” Through the help of Ohm’s law I have found that the number we get after dividing the voltage and the current, is known as the resistance.
As can be seen from the above table, most of the resistance lies around the same number. In the first table for the thin wire, the resistance was around 8-9. In the medium wire it was about 4 and in the last thick wire it was around 0.9. Therefore the formula for finding resistance can be said to be as:
Resistance (R) Ω = Voltage (V)/Current (I)
Also from the tables above, we can notice quite a major thing. For different wires, there is a different amount of resistance. The thinner the wire the higher the resistance there is if the temperature and other physical conditions remain constant. The resistance would remain the same, for each wire, no matter how EMF is supplied. From my results, it can be seen that the results are around the same for each wire, but there are some which differentiate. The reason could be the temperature, which we might not have kept constant. As it is a classroom, the air-conditioner and the amount of people in the class, keep changing the temperature, and also the higher the EMF the hotter the wire will get and hence there is a difference in the temperature. Therefore the temperature is affected.
Hence the relationship between the current through a resistor and the voltage across it, is positive, and they are both directly proportional.
Evaluation:
From the three graphs we can see that most of the points lie around the best-fit line, thus the results seem reliable but still there are some possible errors, which could have occurred while I was performing the experiment. They are as written below:
- Circuit was not connected properly.
- Limitations of the Voltmeter/Ammeter.
- Temperature Variable not kept constant.
- Taking the reading could have been wrong.
- The length of the Nichrome wire could be different thus increasing or decreasing the resistance.
Below I have listed some of the ways in which these the above errors could be removed:
- (for error 1) could have checked the circuit several times, and confirmed it by the teacher also.
- (for error 5) before starting the experiment, it could be kept in mind to keep the wire the same length by measuring it.
Above I have written the ways to improve some of the errors. Error 2 cannot be improved, upon because the school doesn’t have a voltmeter/ammeter which could go above a specific range and thus it didn’t give us specific results for the thick wire we wanted. Error 3 cannot be improved upon because keeping the temperature constant with so many people in the room is not possible. Error 4 cannot be improved upon as there always has to be some human error. No human is 100% perfect, and thus not all errors can be removed. But they can be improved upon, and reduced to a certain limit.
To further extend this experiment, we could do the following:
- Use a variety of thickness of wires.
- Using other materials other than a Nichrome Wire in order to test resistance.
- Testing other variables like the effect of temperature on resistance.
- By improving upon the errors.