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Practical electricity experiment questions

Q1.

(a) A student is given a piece of metal wire and asked to investigate how the resistance of the wire changes between a temperature of 0 oC and 100 oC.

(i) Draw a labelled diagram of a suitable arrangement that would enable the student to carry out the experiment.

circuit with ammeter in series with the wire and a voltmeter in parallel with it

some means of heating the wire (eg water bath)

thermometer immersed in the water bath

(3 marks)

(ii) Describe the procedure the student would follow in order to obtain accurate and reliable measurements of the resistance of the wire at different temperatures. The temperature range should be between 0 oC and 100 oC.

This is marked as to how well you communicate as well as knowing what to do. Your English needs to be good and you must clearly explain what you are going to do and how you will use data obtained.The explanation expected in a competent answer (5 or 6 marka) should include a coherent selection of the following points:

  1. water bath method used - wire encased in insulator (plastic bag) and immersed in a beaker of water.
  2. ice added to water until it reaches zero degrees.
  3. water stirred
  4. and the temperature measured with thermometer
  5. switch closed on the circuit
  6. current and p.d. noted down
  7. resistance calculated as V/I
  8. bunsen used (or electrical heater used) to raise the temperature ten degrees then to point 3 on this method list again until water is 100 degrees Celsius.
  9. Graph drawn of Resistance (y-axis) against temperature (x-axis) (Leaving this out gets you a maximuim of 4 marks - how the results are used to illustrate the relationship is important)

(6 marks)

(b) A certain metal has a critical temperature of –268 oC (5 K). Explain what is meant by critical temperature.

The critical temperature is the temperature at or below which a material becomes a superconductor i.e. has zero resistance or resistivity.

(2 marks)

(Total 11 marks)