Length of the wire – The longer the wire, the more the electrons have to travel, thus increasing resistance.
Temperature – When the temperature of a metal is increased, the metal ions inside vibrate more, and so the electrons which are moving through have a higher chance of hitting a moving metal ion rather than a stationary one.
Material of the wire – Nichrome and Copper are two wires. Copper has low resistance, which means electrons move freely within it, but nichrome has high resistance, therefore electrons inside move more slowly as there is a higher concentration of metal ions.
Resistance cant be measured directly. It varies all the time, but we can make an approximate estimation by using the following formula:
Resistance = Voltage (V)
Current (A)
Preliminary Work
The Thickness of the wire will have to be varied, as we are going to be using more than one wire, all different thicknesses, with diameters large and small.
The Length of the wire will have to be measured every time we make a new record on our table, to see how resistance increases/decreases every few centimetres (cm). Also the value of the current will be measured to check up on the amount of resistance generated by the wire and the electrons.
I will mention Ohm’s Law here, as it defines the relationship between power, voltage, current and resistance. The unit for resistance is (Ω) Ohms. In Ohm’s law, if the circuit has constant resistance with unvarying temperature, the current rises at a constant speed. The voltage across the conductor is directly proportional to the current, and this is usually written as:
V = IR
Whereby V is the Voltage, I is the current and R is the resistance.
I expect the resistance of the wire to increase with the length of the wire. So, for example, if the length of the wire is increased, then so will the current, as the electrons will have a longer way to travel through the wire.
For preliminary work, we found out the voltage and the current of 3 different types of wire material. They were:
Nichrome
Constantan
Copper
The different types of material look out how much resistance is generated by the material of the wire. As you can see, constantan has the highest amount of voltage and current, therefore meaning low resistance. The longer the wire gets, the more resistance there is as the electrons fight their way through the metal ions.
Copper has the lowest voltage and the lowest current out of the 3, so its resistance is very low and can be dangerous to work with.
Nichrome is the best material to work with as it has got the highest resistance and is workable with.
For my investigation, I will expand on the work I have done with the nichrome wire but with longer length to prove my prediction is correct.
Wire = Nichrome
This table shows me that that the thicker the wire gets, the higher the resistance, and because there were 4 thicknesses it shows everything in good accuracy. These values can be inaccurate because of some factors.
- The diameter of the wire could not be measured thoroughly enough because it gets too small for equipment to measure.
- There is a smaller range, so its not accurate enough, whereas with lengths, you can measure as many as you want.
- In my investigation I will use 30 SWG for my thickness of nichrome wire.
This atomic model for resistance in a metal depicts a nucleus surrounded by negatively charged electrons. In solids (wire, etc), the outer electrons of each atom form a bond between them that hold the solid together, and in a metal these bonding electrons are free to move about throughout the solid, and when a voltage sends its current through the metal, the electros start to move about, following the current.
