Electricity Investigation

Ohms is used to measure resistance. Ohm's law is:-

" the current flowing through a metal wire is proportional to the difference across it (providing temperature remains constant)"

This means that if you double the voltage then the current is doubled. E.g.

Wires contain a resistance in them. The more resistance there is the more voltage needed to push the current through the wire. Resistance of a wire is made calculatyed by:-

Resistance, R = Voltage (V)

Current (I)

There are four main factors affecting resistance in a circuit:

. As length increases, so does the resistance.

2. As cross sectional area increases, the resistance decreases because the flow of charge has a greater passage to travel through.

3. The metal you use. Copper is a good conductor and is used for connecting wires. Michrome has more resistance.

4. As temperature increases, the resistance increases of a wire. This is because heat causes kinetic energy amongst the electrons. So as they began to vibrate and move this makes it more difficult for a clear flow of charge and adds to resistance.

I predict that as the length of the wire increases there will be more resistance so the current will need a greater amount of voltage.

I will attempt to collect at least 3 sets of data to discover any anomalous and to gain a wide range of results.

When conducting experiment I will have to take certain safety measures such as :-

* Wearing gloves due to working with circuits

* Be careful of sharp wires

* Be careful with any heavy equipment

The variables that I will keep fixed is the temperature of the wire, the cross sectional length of the wire, and the metal of the wire. There are also things such things like the components that I shall use, weather it be the amount of bulbs and batteries.

My variable in the experiment will have the most affect on resistance and will be able to conduct a good experiment with good results and understanding.

Apparatus:- wires ( 6-8), 2 batteries, 1 bulb, digital ammeter, digital voltmeter, switch, variable resistor.

A voltmeter is used in parallel circuits and will measure voltage, the ammeter is in a series circuit and will measure amperes.

With my equipment I shall choose digital equipment as they gave an accurate reading to 0.01.

Method_:-

) Begin by gathering all the equipment that you may need.

2) Attach the wires accordingly to construct circuit,

Attach the 2 batteries together with 1 wire.

3) From the second battery attach a wire and add an ammeter

4) From the ammeter with another wire attach a bulb. Then again with another wire attach a switch from a bulb.

5) To complete the circuit add another wire from the switch to the variable resistor, and then from the other end of the variable resistor add another wire to the free part of

the battery.

6) To add the voltmeters add a parallel circuit from the bulb with another 2 wires.

7) After the circuit is complete take your measurements. Do this by taking the free end form the battery and moving it along the circuit every 5 cm and take the readings from ammeter and voltmeter. Repeat 3 times.

To make this a fair test I will have to: -

* Use gloves when conducting the experiment because the moisture in your finger will act as an insulator

* Take accurate readings to obtain proper results.

* Make sure wire reaches its proper point

* Make sure that the batteries are new so that there will be equal voltage and the current will not have an unequal strength.

* Make sure that the wires are made of the same material.

* Make sure that the temperature of the wire is the same as the surroundings and not any higher because the temperature can affect resistance.

* Make sure that the components are not faulty.

* The resistance in the wires are the same

Results

My results have shown that as the length of the wire increases more voltage is needed around the current.

More voltage is needed because charge needs to flow around the circuit and as it covers a greater distance the resistance becomes stronger so a greater push is needed. So as length increases, so does the resistance.

My results have matched prediction in that as the length of the wire increases as the voltage increases as there is more energy needed for charge to flow around the circuit.

For example at cm the readings was . This proves that when there is a greater length there is more voltage needed for charge to flow and that resistance will occur when the wire length is longer and thinner.

EVALUATION

In convulsion my prediction has matched my final results. My method did provide a reasonably reliable set of results but did provide a few anomalous results. A reason to why this may of happened is because the readings may not of been taken down accurately, the resistance in the wire was not the same or the experiment was not conducted properly. The final results were the most inaccurate aspect to the experiment. The key variables were controlled. From this experiment I have learnt that as length of wire increases so does the resistance of the wire.

To improve the experiment next time I could possibly try different measurements, conduct experiment more scientifically, vary components, and change the key variables. Points for further investigation are into the key variables and conduct more experiments on them and how they add to resistance.

I would like to comment that this experiment has made me more aware about the factors that involve resistance and I have gained in knowledge about circuits and how to conduct experiments with circuits.