Question 18M.3.SL.TZ1.2
| Date | May 2018 | Marks available | [Maximum mark: 6] | Reference code | 18M.3.SL.TZ1.2 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Draw, Explain, Outline | Question number | 2 | Adapted from | N/A |
An experiment to find the internal resistance of a cell of known emf is to be set. The following equipment is available:
Draw a suitable circuit diagram that would enable the internal resistance to be determined.
[1]
ammeter and resistor in series
[1 mark]
It is noticed that the resistor gets warmer. Explain how this would affect the calculated value of the internal resistance.
[3]
resistance of resistor would increase / be greater than 10 Ω
R + r «from ε = I(R + r)» would be overestimated / lower current
therefore calculated r would be larger than real
Award MP3 only if at least one previous mark has been awarded.
[3 marks]
Outline how using a variable resistance could improve the accuracy of the value found for the internal resistance.
[2]
variable resistor would allow for multiple readings to be made
gradient of V-I graph could be found «to give r»
Award [1 max] for taking average of multiple.
[2 marks]