Resistance Of Wire
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IF YOU INCREASE THE VOLTAGE – MORE CURRENT WILL FLOW.
IF YOU INCREASE THE RESISTANCE – LESS CURRENT WILL FLOW (UNLESS YOU INCREASE THE VOLTAGE).
у`In Metals The Current Is Carried By Electrons
1. Electric current will only flow if there are charges, which can freely move.
2. Metals contain a sea of “Free Electrons” (which are negatively charged). And flow throughout the metal if they are given energy.
3. This is what allows electric current to flow so well in materials.
у`Resistance
Resistance is anything that causes an opposition to the flow of electricity in a circuit. It is used to control the amount of voltage and /or amperage in a circuit. Everything in a circuit causes a resistance (even wire). It is measured in OHMS (Ω). Resistance occurs when the electrons travelling along the wire collide with the atoms of the wire. These collisions slow down the flow of electrons causing resistance. Resistance is a measure of how hard it is to move the electrons through the wire. The resistance of a wire depends on the number of collisions the electrons have with the atoms there will a larger number of collisions which will increase the resistance of the wire. If a length of a wire contains a certain number of atoms, when that length is increased the number of atoms will also increase.
E.g. If there is a wire that is half the length of another wire it would also have half the number of atoms, this means that the electrons will collide with the atoms half the amount of times. Also if the length of the wire is trebled or quadrupled then the resistance would also treble or quadrupled.
My prediction was derived from this information.
All of this information I collected originated from the Website, “www.studentcentral.co.uk” from encyclopaedias such as “The Oxford Childrens Encyclopaedia” and computer encyclopaedias such as “Encarta”.
уThis scientific information relates to my experiment by stating that the longer the lengths of wire the higher the resistance.
уPreliminary Results
Length Of Wire (mm):
Voltage (V):
Current (A):
Resistance (Ω):
уTherefore this information supports my prediction that the longer the length of wire the higher the resistance.
Obtaining Evidence:
уThe variables I kept the same are:
Ñ„The same material used for the wire,
Ñ„The same cross-sectional area of wire,
Ñ„And the same temperature of the wire.
уThe potential difference from the power pack: 2V.
уThe current, which measured the rheostat, was kept at: 0.5A.
уThe lengths of the copper wire:
If the diameter of the wire was wider then more electrons could get through therefore less resistance. So the thicker the wire the lower the resistance because there is a bigger area for the electrons to travel through, so there will be less chance of them colliding into one another which means there will be less energy produced.
I predict the longer the wire the higher the resistance and the shorter wire the lower the resistance. I think this because the longer the piece of wire the further the electrons have to flow, then that would mean the more collisions with atoms, which would increase the energy therefore increasing the resistance. Also if I double the length then I double the resistance. The electrons start of with kinetic energy they then collide with other electrons, which is then transferred to heat energy.
I think that the shorter the wire the lower the resistance because they have less of a way to travel which means they wont collide with as much atoms, therefore less energy will be produced.
Background Info:
Resistance 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 of an electric light bulb.
Record this reading on your table. The table should have a space for Length and Current.
5. Now shorten the length of the wire slightly by changing the position of the crocodile clips, maintain the voltage using the variable resistor, and jot down your reading from the ammeter.
This procedure should be repeated until you reach the minimum length. (The minimum length will be discussed in the preliminary section later on).
To ensure that obtain a good quality of results