To investigate the resistance of different materials in the form of wirer, resistors and other materials.

Safety Measures:

While electricity is dangerous and should be respected, it is important to understand how to with handle it to avoid a shock. Be careful not to leave the circuit on too long and try to avoid touching the resistor and wire as it will get very HOT and can even burn into tables. Make sure that the circuit is properly connected before turning the power supply on, and do not touch the apparatus, especially the tested, naked wires until the power is switched off. The changing of the tested wires should only occur when the power is off. Do not switch on the power pack when there is no resistant wire and do not turn the power supply up too high because wires will melt.

Planning B:

The Equipment needed:

• A variable DC power pack
• Ordinary wires
• An ammeter
• A voltmeter
• Crocodile clips
• Wires for tests
• Bulb
• Thermo resistor (rheostat)
• Resistor

Method:

• Connect the wires to the circuit by the crocodile clips
• Take the voltage and current readings from the meters
• Increase/decrease the supply from the power pack and take the readings again
• Repeat the experiment with different materials, wires, bulbs, resistors

Results:

Wire:

Bulb (variable resistor used):

Thermoresistor:

Resistor:

Graphs:

Thermo resistor (rheostat):

Resistor:

Conclusion:

R = V/I

Resistance (ohms) = Voltage (Volt) / Current (ampere)

The larger the resistance, the greater the gradient will be. Gradient of the graph gives the value of resistance. Ohm's law does not always apply. A light bulb in place of the resistor in the circuit gives a different pattern for the current and voltage relationship, as shown in the graph. Here the current and voltage are not proportional. The bulb obviously gets hotter and hotter. Since "resistance" is measured by the gradient of the graph, we have here an example where the resistance is increasing.

But obviously we are dealing with "normal" resistors in this investigation, so the gradient of the graphs obtained should be the same throughout linear and the resistance should remain constant as the voltage/current is changed.

Evaluation:

• To get better results the following things should be done:
• The power supply should be varied smoothly  between 0-12V with 0.1V interval so more averaged results can be taken.
• Temperature has to be absolute constant to create a fair test. Otherwise Ohms law will not apply.
• Better quality equipments should be used.
• More accurate Meters