This graph is measuring the
circuit through a resistor. It
shows that the current (I) is
proportional to the voltage
(V). This is Ohm’s Law. The
steeper the graph the lower
the resistance. The flatter
the graph the higher the
resistance.
Method:
I am going to change the input of volts using a variable resistor, and then measure the current using an ammeter. Finally I will work out the resistance by dividing the voltage by the current.
To make this a fair test the background temperature of the room will be kept the same and I will let the bulb cool down after each test.
1. Firstly I am going to collect the equipment which consists of; a cell, an ammeter, a voltmeter, a variable resistor and a bulb.
2. I will then connect all the equipment making a parallel circuit.
3. Lastly I am going to record the current that different inputs of voltage give me then calculate the resistance.
Diagram:
Prediction:
If the voltage is increased I predict that it will affect the current by making it rise. Eventually the current will level off because there is a bulb in the circuit. Due to the movement of electrons going through it, the thin wire in the bulb will resist more. The wire has a certain resistance to the current because the greater the resistance, the more voltage is required to push a current through a wire. Because more volts are being fed, the current will start to level off as a result of the electrons getting hotter which gives more resistance.
Results:
Graph:
The graph is not a straight line therefore I know that the bulb is a non-ohmic conductor. It doesn’t obey Ohm’s Law.
The metal filament gets hotter as more current flows and so its resistance increases. As shown above, this means that the graph gradually gets flatter.
Conclusion:
My prediction was correct. When a bulb is added to a circuit, the current levels off, due to the resistance caused by the electrons getting hotter in the wire filament of the bulb. This also means the resistance increases. When there is no bulb in the circuit the resistance stays the same.
To improve my experiment I could have repeated the experiment to work out average results. By doing this it would make the experiment more accurate by eliminating any mistakes or anomalous results.
