Investigating how the length of a piece of wire affects resistance in a circuit.

Authors Avatar

Stephanie Wickers                                                        1st July, 2003

Investigating how the length of a piece of wire affects resistance in a circuit

Aim

Resistance is measurement which describes how difficult or how easy it is for an electron to flow through a conductor in a circuit. Resistance is measured in Ohms.

        In this investigation I am going to be trying to find out and do further research into why resistance is affected by the length of a piece of wire.

Research

        There are many factors effecting resistance in a circuit and the four main ones are Length, Temperature, Material, and Thickness. I have done research to find out how and why these factors affect resistance.

        If the length of the wire is increased then the resistance will also increase proportionally. This happens because the electron has further to travel in the circuit and therefore there is more chance of a collision between an atom and an electron.

        If the thickness of the wire increases then the resistance will decrease and if the thickness decreases the resistance will increase. This is because the increase in area will enable the electrons to move around more freely. This in turn will reduce the number of collisions between atoms and electrons and will lower the resistance as the flow of electrons is not interrupted as much by the atoms in the wire.

        If the wire is heated the atoms in the wire will vibrate due to the increase in energy. This will cause more collisions and higher the resistance. This is because the atoms will be vibrating into the path of the electrons and causing collisions. This increase in collisions is the reason for the increase in resistance.

        The material of the wire will affect the amount of free electrons which are able to flow through the wire. If the atoms in the wire are closely packed the electrons will have more frequent collisions, therefore increasing the resistance. Materials such as copper, which are good conductors, allow a large amount of electron movement, causing a low resistance whereas poor conductors, such as steel, which has a high resistance, has a low free electron movement therefore not allowing a good current flow.

        I know that resistance is affected by the length and thickness of a piece of wire. If the length of the wire is increased, the number of atoms which collides with the electrons is also increased.  This is what causes resistance. If the thickness is increased then so it the space between the atoms in the wire, which means that fewer collisions between atoms and electrons which will decrease the amount of resistance in a circuit.

        The resistance in any material is inversely proportional to the area of its cross section (A):

R=1/A

Ohms law is a law on resistance which enables us to work out different quantities in a circuit. It says that the current flowing through a circuit is proportional to the potential difference across it as long as the temperature is kept constant.

RESISTANCE (R)

CURRENT THROUGH THE WIRE (I)

R= V/I

I= CURRENT IN AMPS

RESISTANCE IN THE UNIT OHM

When rearranged the formula can look like this depending on what needs to be calculated.

I=V/R

V=IxR

Investigating length on resistance 

                Metals conduct electricity because the atoms in them do not hold their electrons very well, which create free electrons. These free electrons are negatively charged and collide along the line of atoms in a wire. Resistance is caused by these free electrons flowing towards the positive terminal collide with atoms. If we double the length of wire the number of atoms doubles so the number of electrons colliding also doubles so twice the amount of energy is required. There are twice as many collisions if the wire is twice as long. This occurs because the positively charged atoms are flowing towards the negative terminal and the negatively charged atoms are flowing towards the positive terminal. This causes collisions and in turn resistance.

Join now!

Prediction

        I predict that if the length of the wire increases then the amount of resistance in the wire will also increase. I think that the resistance will increase proportionally to the increase in length of the wire. I think this will happen because the longer the length of wire the more atoms there are and this means that there is more chance of a collision. If a length of wire is 5cm long and the resistance was 1.5 Ohms then if the length was doubled the resistance should double to about 3 Ohms. This is because there will ...

This is a preview of the whole essay