Aim: To alter the length of wire and measure the effect on the resistance.
Apparatus: 3 wires of widths 28, 30 and 36.
1 ammeter - to measure the current in amps
4 crocodile clips - attach to the wires
6 leads - use to connect circuit
Ruler - to measure length of wire
Masking tape - measure and tape against the ruler
Power pack - supply energy in volts
Volt meter - measure the voltage in volts
Variable resistor - control the resistance
Brief: First I will carry out a pre-test where I will test the 3 widths and then choose one that has the lowest resistance meaning it has a higher current. Once I have completed the pre-test, I will carry out the experiment. I will change the length of the wire about 5 times each at 5 different volts for the input. I measure the output voltage using a voltmeter and the current using an ammeter.
Variables to keep fair test:
ÃÂ·Length of wire - input
ÃÂ·Resistance - it will be kept the same
ÃÂ·Voltage - will alter
ÃÂ·Current in amps - output
ÃÂ·Width of wire
ÃÂ·Type of metal for wire
Metallic bonding theory
e- e- e-
+ + +
Free electrons move e- e- a sea of electrons
When pushed by volts + +
e- = Delocalised electrons
+ = Metal cation
As the metal cations and the electrons are oppositely charged, they will be attracted to each other, and also to other metal cations. These electrostatic forces are what hold the particles together in metals.
Metallic bonding is present in all metallic elements. Positive ions of the metallic element form a giant lattice (regular arrangement), with the valency electrons floating over them. This means that the electrons...