The aim of this is to investigate how the length of a wire affects the resistance of it.
Resistance is a force, which opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. The circuit itself can resist the flow of particles if the wires are either very thin or very long. E.g. the filament across an electric bulb is quite thin as needs to resist the flow of particles for the bulb to glow.
Resistance is measured in ohms. .
George Ohm discovered that the voltage of a circuit is directly proportional to the current flowing through the circuit. This means that if you triple one, you triple the other. He also discovered that a circuit sometimes resists the flow of electricity. He called this resistance. He then came up with a rule for working out the resistance of a circuit:.
V/I = R.
V - Volts.
I - Current.
R - Resistance.
Below are the facts that I need to consider when investigating the resistance of metals:.
1. Electrical conductivity involves movement in charged particles. An electrical current means they are Mobile Charged Carrier.
In metals this means moving electrons. In graphite (carbon) the current is due to the electrons. If the particles aren't charged or have no movement then the material is an insulator e.g. plastic, rubber or solid salt.
Solid salt contains charged particles, which are called ions, but these are not mobile in its solid state:.
2. Resistance to the current is due to the electrons trying to get past the atoms. When metals get heated the particles within begin to move more and there is more resistance to the flow of electrons.
3. Ohm's law describes the relationship between electrical resistance, current and voltage:.
4. Semi conductors e.g. as in thermister.
5. The variables that control the electrical resistance of a piece of wire:.
Plan:.
I will have to measure out lengths of nichrome wire, all of the same type of thickness, and keep them at the same temperature (to keep the experiment reliable and precise) .