Safety
There are no serious safety precautions for this experiment, however, I will make sure that the voltage does not exceed 10-12V as this may cause the Meyer Lamp to blow.
Accuracy
I will carry out the experiment three times so no obvious mistakes will be made. The accuracy with which I can determine the current depends on how many significant figures the ammeter will read them to. This can be altered by the settings and I will choose to keep the accuracy of the current to 2 significant figures. The Voltage will remain a whole number.
Precision & Sensitivity
The ammeter will have precision of 0.01 Amps.
The voltmeter has a precision of 0.01 Volts.
The voltage from the power supply has precision of 1 volt.
The sensitivity of the ammeter is quite reasonable for this experiment as it will give me quite accurate results. Having a greater precision may cause problems in plotting a graph.
The sensitivity of the voltmeter is accurate for this experiment as it will be only increased by 1 volt each time.
Theory
Current is the flow of charge and voltage is the electrical energy converted per unit charge.
The main relationship between current, voltage, and resistance is called Ohm's Law, discovered by Georg Simon Ohm. Ohm's principal discovery was that the amount of electric current through a metal conductor in a circuit is directly proportional to the voltage impressed across it, for any given temperature. Ohm expressed his discovery in the form of a simple equation, describing how voltage, current, and resistance interrelate:
V = IR
Where V is the voltage in volts, I is the current in amps and R is the resistance in Ohms.
According to Ohm's Law there should be a linear relationship between the applied voltage and the resulting electrical current but there are environmental factors such as temperature or material characteristics of the resistor that may produce a non-linear curve. In other words, the current is directly proportional to the voltage.
Diagram
Observations
I recorded my results in the table below.
Analysis
The above graph shows a strong positive correlation between Current and Voltage. It clearly shows that as the voltage increases so does the current. The graph is linear, hence the current is directly proportional to voltage. This agrees with Ohm’s Law. The line of best fit shows that there are no obvious anomalous results. This may be because I repeated the experiment three times and took an average.
Evaluation
For this experiment I conclude that currently is directly proportional to the voltage supplied. This result agrees with Ohm’s Law and so Georg Simon Ohm’s theory is proven to be correct.
According to the graph I can say that my experiment went reasonably well. However, not all the points lie in a perfect straight line. This may be because temperature was a factor that was hard to control in this experiment. The best we could do was to work at room temperature. The variable temperature did not produce any major anomalous results and so the error can be said to be very small.
The graph shows that as you increase the voltage the current also increases. I increased the voltage in the experiment by decreasing the resistance, therefore more current was allowed to flow through the circuit and so there was a greater potential difference between the Meyer Lamp.
As the experiment shows that there was a current-voltage relationship of the lamp, we can call the lamp an “Ohmic” material as V=IR.
