Research Question: how temperature affects the conductivity and resistance of a wire?

Aim: To investigate how the change in temperature of the wire affects the resistance of the wire.

Background Information: Resistance is when electrons travelling through the wire are impeded by the atoms within the wire. Since the electrons are charge carriers when they collide with the atoms in the wire, less pass through. Therefore less current passes through with the same voltage. Simply it is how hard it is for the electrons to pass through the wire. The main factors responsible for affecting the resistance of a wire are temperature of the wire, length of a wire, cross-sectional area or width of the wire and the material of the wire. Electrical conductivity measures the ability of a conductor to allow current to flow in it. Therefore conductivity is the inverse of resistance. The higher the resistance of the wire, the lower the conductivity will be.

Resistance = 1 / Conductivity

Ohm’s Law states that when a current I ampere flows inside a conductor of resistance R ohms, the voltage V volt across the wire will be the product of the current and the resistance.

Voltage V = Current I x Resistance R

Hypothesis: When the metal wire is heated, more energy s given to the atoms, therefore they vibrate more. From this there is a greater chance of collisions with the electrons and they are impeded more, therefore less charge is passed by the electrons and the resulting current

is reduced. I predict that as the temperature would increase, the kinetic energy of the atoms, of the wire, would increase, increasing the resistance. Since there would be more random collisions between atoms of the wire, per unit time, there would be less space for current to pass through, hence increasing the resistance.

Variables:

Independent- TemperatureTemperature would be kept as the independent variable as it needs to be varied in the experiment to now if it actually affects the resistance of the wire. The temperature, which is the independent variable, will be marked on the x-axis.

Dependent- Resistance The resistance of the ire is the dependent variable because it depends on the independent variable which is the temperature of the wire. The dependent variable will be marked on the y-axis.

Controlled- Material of the wire, Length of the wire, Cross-sectional area or width of the wireAll the other factors that can affect the resistance of the wire except temperature need to be kept constant as, if any of them is changed, the results will vary and we will be distracted from our aim. Our results will become hampered.

Apparatus:

EQUIPMENT QUANTITYWire A 40cm3

Connecting wires 4 to 5

Cells 4Ammeter 1Voltmeter 1Measuring Cylinder 1Switch 1Beaker 1Spirit Lamp 1Tripod & Gauze mat 1Water 200ml

Diagram:

Method:1. Collect all the equipment and set up the apparatus in the way shown

above in the diagram.2. First pour 200ml of water (20°C) in the beaker using a measuring

cylinder.3. Once the wire is in the water, turn the switch on.4. Then record the readings of the ammeter and voltmeter. Perform

three trials and record these readings as well.5. Now, repeat these steps by changing the temperature of the water,

by heating the temperature to 30°C, 50 °C, 70°C, and 90°C.6. Finally change the water and put ice measuring 0°C in it instead.7. Once you get the readings , take the average of each trial and find

the resistance of the wire at each temperature using the formula( V/I which is Voltage/Current)

Temperature (°C) Trial Voltage – Current-I/ A Resistance- Ω Average

No. V (Volts) (Ampere) (Ohms) resistance

0°C

Trial No. 1

4.5 8.72 0.516

0.514 ΩTrial No. 2

4.5 8.76 0.513

Trial No. 3

4.5 8.73 0.515

20°C

Trial No. 1

4.5 9.82 0.458

0.459 ΩTrial No. 2

4.5 9.78 0.460

Trial No. 3

4.5 9.81 0.459

30°C

Trial No. 1

4.5 9.43 0.477

0.479 ΩTrial No. 2

4.5 9.36 0.481

Trial No. 3

4.5 9.42 0.478

50°C

Trial No. 1

4.5 8.81 0.511

0.511 ΩTrial No. 2

4.5 8.84 0.509

Trial No. 3

4.5 8.79 0.512

70°C

Trial No. 1

4.5 8.43 0.533

0.535 ΩTrial No. 2

4.5 8.40 0.535

Trial No. 3

4.5 8.36 0.538

90°C

Trial No. 1

4.5 8.01 0.562

0.564 ΩTrial No. 2

4.5 7.97 0.565

Trial No. 3

4.5 7.93 0.567

Analysis and Conclusion: At the end of the experiment, after looking at the results, I know that my hypothesis was correct. At the temperature increased, the resistance increased due to the collision theory. But due to the same theory, the resistance increased when the temperature was near 0 degrees Celsius. The temperature of the wire increases due to its power loss, which is calculated as I2x R., where I is the current in the wire and R is the resistance. The higher the current in the wire or the higher resistance will cause the temperature of the wire to increase. Therefore it is important to choose the correct wire sizes to minimize this unwanted loss and reduce the temperature of the conductor. When the experiment is repeated with the coil in a water bath so that its temperature remains constant, the characteristic graph is a straight line, showing that the resistance remains constant. Pure metals do obey Ohm's law when their temperature remains constant. Wires made from alloys such as Constantan or Eureka wire (consisting of 60% copper and 40% nickel) are designed to have a very small temperature coefficient of resistivity. Therefore, they do not need to be placed in a constant temperature bath in order to show ohmic behavior.

Evaluation: After evaluating my hypothesis, I came to a conclusion that my hypothesis could have been more detailed and it did help me during the evaluation of the data that I got. The method I used could have been expanded and written in a safer method. Instead of using a spirit lamp, I could have gotten heated water from the biology laboratory. This would have saved my time as well. For better results, I could have tried doing more trials or should have taken more temperatures. I could have also tried adding an extra ammeter or voltmeter to make sure that my apparatus wasn’t faulty and it wouldn’t give me incorrect readings.