Investigation To Show How Resistance Is Affected By Length.

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Investigation To Show How Resistance Is Affected By Length

Plan of Action

In order to investigate “how resistance is affected by length” I will need to:

  • Present my aim
  • Show scientific knowledge relevant to the topic
  • Consider my hypothesis
  • Produce a list of apparatus required for my experiment
  • Consider an appropriate method
  • Show considerations of Safety
  • State the possible variables in my experiment
  • Show attention to accuracy
  • Include a circuit diagram
  • Decide on a clear method to show data  for example a results table, graph with line of best fit and error boxes
  • Analyse my results
  • Make a conclusion based on my results
  • Evaluate against my original intentions for my investigation

My Aim

My aim is to use conducting putty to investigate any possible relationship between the resistance of an object and its length.

Scientific Knowledge

Resistance determines how easily a charge can travel through a circuit. The higher the resistance the harder it is for the charge to flow through a circuit and visa versa. The longer the length the higher the resistance, this is due to there being more particles to slow down the flow of electrons (charges). The amount of charges will half when the length is halved. We know that resistance is inversely proportional to length and also to the cross sectional area. Therefore, putting these 2 together we get resistance being inversely proportional to length/ cross sectional area:

 Resistance =            length          .

                     Cross sectional area

Hypothesis

I predict that my results will show that resistance is directly proportional to length. Furthermore, I think that I will find the longer the length of putty the higher the resistance. As I cut the putty down I will expect the resistance to decrease.

Apparatus

  • Conducting putty
  • Knife/scalpel
  • Ruler
  • 4x4 cm copper square
  • Wires
  • Multi-meter
  • Micro-meter
  • Crocodile clips
  • Safety Goggles

Method

Firstly, I will clear a space on a desk top, and remove anything that might be an obstruction and gather my equipment. Secondly, I will put on my safety goggles and gloves and make my putty into a cylindrical shape with my hands. It will be 10cm (0.1m) in length and have a width of 3cm (0.03m) this will be measured by using a ruler to the nearest (mm). After that, I will connect the circuit consisting of a multi-meter, two copper squares each side of the conductive putty and two wires and crocodile clips connecting them all together. Before adding the copper squares to the circuit I will put HCl (as this will remove the oxide layer) onto them to make them more conductive. I will switch on my multi-meter and take a reading. This will be recorded in a table and then taken again for a second reading. I will measure 1cm with my ruler and remove that amount. Once I have done so using a knife and taking care I will measure the putty again to see that the correct length has been removed. This will be repeated until a length of 1cm has been reached and the resistance recorded. Once done so I will find the average reading for the resistance in ohms and make a graph showing my results.

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Safety

To ensure my safety I will make sure I wear safety goggles and gloves. I will be wearing safety goggles as I may use HCl to clean the copper squares and, therefore, make them more conductive.

Accuracy

For accuracy I will make sure that when I measure the length and cross-sectional area of the putty the scale of the ruler is in line with the end of the putty. Also, I will take the readings to +/- 1 mm at each end of the putty this will take into account any errors.

When I am ...

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