Resistance is anything that slows the flow of electrons (current) down in a circuit. Resistance is measured in ohms, W. As resistance is increased less current will flow. The total resistance in a series circuit is sum of all the resistances
Ohm's law is the mathematical relationship between the voltage, current and resistance in an electric circuit. This law states:
Voltage (V) = amps (I) x Ohms (R)
V=IR
The relationship between heat and resistance is demonstrated by the fixed resistor and filament light bulb experiments. When a filament light bulb is used more heat is created than when a fixed resistor was used. Therefore the filament light bulb graph has a curve, while the fixed resistor graph produces a straight line. In these graphs resistance is the gradient or voltage (v)/ current (I).
In a series circuit all the components are connected in a line between the positive and negative terminals. The voltmeter is the only exception as it is always connected in parallel. If one part of the circuit is removed or disconnected the circuit is broken and nothing in the circuit will function until the circuit is complete again.
After finding out the information I predict that the larger the area the easier it will be for the electrons to move through it as there are less electrons to collidie with each other which is what causes the resistance.
Variables:
In my research I have found several variables that would affect the resistance of a piece of wire. The variables that can affect the resistance of a piece of wire are:
- Diameter.
- Length.
- Temperature.
- The material.
I intend to choose one variable to investigate thoroughly, but I will briefly examine the other variables, giving quantitative predictions of resistance in proportion to that variable.
The variable thaty I choose to investigate is the thickness of the wire
Safety:
As electricity is being used care must be taken to positive terminals, negative terminals or bare wires must not be touched when the power supply is on. The resistance wire may heat up as electricity is passed through it so this piece of wire must not be touched will the power supply is on.
Method:
1. Set up the apparatus as shown
2. Measure the required length of wire (50cm)
3. Place crocodile clips onto either side of the wire
4. Turn on the power supply (2V)
5. Set power pack to lowest setting
6. Take readings from ammeter and voltmeter and record in a table
7. Repeat steps 2 - 6 for the other volumes of wire
8. Repeat each experiment 3 times and record results
9. When all results are collected find the resistance by dividing V/I
10.After finding the resistance for the 3 sets of results find the average resistance and record in a table.
11.Plot a graph with volume of wire on the x-axis and average resistance on the y-axis.
Reliability of Evidence:
Digital voltmeters and amp meters were used throughout the experiment. This digital equipment gave a much more accurate set of results. The straight line graph I produced was not an exact straight line, this was due to some of the digits on the amp meters and voltmeters fluctuating so I was forced to estimate the values. Within the circuit the connecting wires offered some resistance, which added to the resistance of the wire. This may have caused slight changes in the results. Crocodile clips are 4/5 mm in size. Therefore the lengths of resistance wire may be inaccurate.
