Resistance in a Wire

Resistance in a Wire

Introduction:

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Metals conduct electricity because the atoms in them do not hold on to

their electrons very well, and so creating free electrons, carrying a

negative charge to jump along the line of atoms in a wire. Resistance

is caused when these electrons flowing towards the positive terminal

have to 'jumps' atoms. So if we double the length of a wire, the

number of atoms in the wire doubles, so the number of jumps double, so

twice the amount of energy is required: There are twice as many jumps

if the wire is twice as long.

The thinner the wire is the less channels of electrons in the wire for

current to flow, so the energy is not spread out as much, so the

resistance will be higher. We see that if the area of the wire doubles

so does the number of possible routes for the current to flow down,

therefore the energy is twice as spread out, so the resistance might

halve.

Aim:

To find out how changing the length of the wire changes the

resistance.

Preliminary Work:

I did a preliminary experiment to find out the current and voltage

characteristics using a test circuit. The component was a filament

lamp. I did this to show that if the wires heats up with increased

voltage and current, the atoms inside the wire vibrate which makes it

harder for the electrons to pass through, therefore increasing the

resistance.

This is a test circuit I used. The ammeter measures the current

flowing through the circuit and the voltmeter measures the volts

flowing through the circuit. To work out the resistance I used the

equation V = IR. V - volts, I - current and R - resistance. I plotted

the graph V vs. I. It was a curved graph which showed me that R

(resistance) increased as the filament in the bulb got hotter. I also

found out the longer you leave the cell on, the higher the resistance