# Resistance in wires.

Essay by misscuriousHigh School, 10th gradeA, September 2003

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.

Power pack

Variable resistor

Ammeter

Wire

Voltmeter

Variables to keep fair test:

ÃÂ·Length of wire - input

ÃÂ·Resistance - it will be kept the same

ÃÂ·Voltage - will alter

ÃÂ·Current in amps - output

ÃÂ·Width of wire

ÃÂ·Temperature

ÃÂ·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...