Resistivity Of Wires

Resistivity of Wires



Introduction &
Aim

This is a lab report based on an experiment using Ohm’s Law which final aim is to measure the amount of current that goes through 4 different typesof wire using constant Voltage and measuring 5 times per wire (1.0m,0.9m,0.8m,0.7m,0.6m).

The wires that we will be using are:

• Constantan 30 S.W.G.
• Constantan 20 S.W.G.
•Nichrome 30 S.W.G.
• Nichrome 24 S.W.G.




Theory

What is resistivity? By definition we have that is how much a material opposes to the flow of electrical current through itself. This beingsaid we have different levels of resistivity for different materials.

Ohm’s Law states the following:

• Resistance is proportional to length and inversely proportional to cross-sectional areaof a wire.

Resistivity, according to Ohm is constant and it is measure is given in Ohm-meters (Ω-m), hence we have the formula:



[pic]




Experiment

Equipment:

• 1.2 m of 4different wires (Constantan 30 S.W.G., Constantan 20 S.W.G., Nichrome 30 S.W.G., Nichrome 24 S.W.G.)
• Variable DC power supply
• 2 Multimetres
• 1 meter rule
• 1 Micrometer screwgauge













Set-up:





[pic]



















Procedure

As shown above the first thing is to make a circuit involving parallel and seriesconnections. The D.C. power supply goes connected to both multimiters in which one of them goes in ammeter mode (series connection) and the other one goes in parallel.

Then we need to get the diameter ofthe wire. In order to get the most accurate diameter we need to measure it with the Micrometer screw guage up to 3 times to obtain the average measurement and by doing so reducing the place for error.Next, the power supply is set to 12 V, then using the crocodile clips we connect them to the wire in turn, which is fixed next to the ruler, and we take the readings of the multimiters (which are...