Resistance of a Wire

Resistance of a Wire

The title of our investigation is 'To electrical resistance in wires.

The aim is to find the effect of the length and area of wires on their

resistance.

Resistance is the restriction of the electrons in a wire. Components

in a circuit will resist the flow of current through them. The greater

the resistance in a wire, the smaller the current that flows for a

particular voltage. The more components that are in a circuit (eg.

Lamps, diodes etc), the more resistance will occur. Voltage, current

and resistance are related by the equation:

VOLTAGE = CURRENT + RESISTANCE

V = IR

If we use this formula we can calculate the resistance in Ohms (W) by

the formula

Resistance = Voltage

Current

R = V

I

Components which allow current to run through them are called

conductors, as they conduct electricity. Those which do not are called

insulators. With each conductor the resistance will depend on length

and the cross-sectional area. Resistance is proportional to length (L

: R µ L) and resistance is inversely proportional to cross-sectional

area (A :R µ 1). If we combine these two

A

We get Rµ L. We change this into an equation by introducing a constant

called resistivity. This,

A

other wise known as p, is a number which depends upon the substance.

Therefore R = p L where

A

L is in metres, A in metres squared, R in Ohms, p is in Ohm - metre

(Wm)

My hypothesis is that as the length of wire increases the resistance

in the wire will increase. I think this because the electrons in the

wire have further to go so suffer greater collisions with atoms in the

material. Electrons moving through a short wire only feel resistance

for a short time compared to the longer one. This means its resistance

is less. If you compare the wire to a traffic jam on a motor -it takes