Resistors are components that are made to have a certain resistance. They can be made of a length of nichrome wire. The diagram shows the circuit symbol for a resistor:
In an electrical circuit it is the resistor, not the wires connecting them to the battery, the gets hot. Electrons are being pushed around the circuit by the battery and they collide with the atoms in the resistor. Energy is given to the atoms so that they vibrate faster; this means the resistor is getting hotter.
A resistor has a resistance of one ohm if there is a current of one ampere through it when the potential difference is one volt.
Apparatus list
- One wire (1m)
- Battery pack (1.5v, 3v, and 4.5v)
- Voltmeter
- Ammeter
- Two clips (one fixed and the other slides along the wire
- Ruler
- G claps
- Optical pins connecting wires
- Cello type
Method
- We will fix the wire in the 1 metre ruler with cello tape.
- I will fix the ruler to the table with two “G” claps.
- Then we will fix one optical pin in the length of 0cm.
- The other one will slide along the wire
- We will connect the optical pins into a circuit with voltmeter and ammeter.
- I will connect the circuit into a battery pack (1.5v)
- I will move the second pin
- As I will move it, I will obtain two results, one in the voltmeter and one in the ammeter, for each length between the optical pins
- Copy that results
- We will change the potential difference. In other words, the voltage will change
- Then, with the results, we will calculate the resistance
- I will repeat the steps 6, 7 and 8 with different potential differences (1.5v, already done it, 3v and 4.5v)
Prediction
I predict if we increase the distance between the optical pins, the potential difference will increase and the current will decrease.
Therefore, the resistance will increase (R=V/I) as the current decrease or as the potential difference increase.
Resistance ∝ potential difference
The graph I will expect to have is:
I will mention that as the temperature increase, the resistance will increase too, because the particles will move more quickly, so the resistance will increase. The graph we will expect to get will be like this:
Safety
- I will not use a high voltage for avoid hurts someone
- I will be attentive if the wire become hot
- I will carried out the experiment in a place with no water
Aim
In this experiment I am going to investigate how resistance increase as I increase the distance between the two optical pins that I will fix in the experiment.
The resistance will increase; therefore, the potential difference will increase too, but the current will decrease, because:
R ∝ V
Analysis
In my graph I have a straight line, and the gradient is: 40°.
The gradient says that the increasing rate of the experiment is: 0.175 Ohms/cm, what is the slope, what means that each cm that we increase, 0.175 is increased per each of that cm that was increased.
This is happened because as we increase the potential difference in the circuit, the wire becomes hotter. In other words, the electrons, which are moving around the circuit pushed by the battery, when they arrive to the resistor they collide with the atoms in the resistor. When the energy given to the atoms is increased, the atoms vibrate faster (and they become hotter), so the resistance increase.
Evaluation
From my point of view, my method was really accurate, because the pin that I used for increase the length, was 1mm wide, what means that gives you an error of 2% in the first length that was 5cm because: 5cm= 50mm, so 50mm/1mm= 2 (this is the percentage of the error) and when we increase the length taken, the error decreases. i.e. 10cm/1mm= 1% of error, and it carries on decreasing. So the precision was very good.
Then the result were very accurate, because I took three different measurements for each length, so the average made a very accurate results.
