User interface language: English | Español

Date May 2017 Marks available 2 Reference code 17M.3.SL.TZ2.2
Level Standard level Paper Paper 3 Time zone Time zone 2
Command term Explain Question number 2 Adapted from N/A

Question

The circuit shown may be used to measure the internal resistance of a cell.

M17/4/PHYSI/SP3/ENG/TZ2/02

The ammeter used in the experiment in (b) is an analogue meter. The student takes measurements without checking for a “zero error” on the ammeter.

An ammeter and a voltmeter are connected in the circuit. Label the ammeter with the letter A and the voltmeter with the letter V.

[1]
a.

In one experiment a student obtains the following graph showing the variation with current I of the potential difference V across the cell.

M17/4/PHYSI/SP3/ENG/TZ2/02b

Using the graph, determine the best estimate of the internal resistance of the cell.

[3]
b.

State what is meant by a zero error.

[1]
c.i.

After taking measurements the student observes that the ammeter has a positive zero error. Explain what effect, if any, this zero error will have on the calculated value of the internal resistance in (b).

[2]
c.ii.

Markscheme

correct labelling of both instruments

 

[1 mark]

a.

V = E – Ir

large triangle to find gradient and correct read-offs from the line
OR
use of intercept E = 1.5 V and another correct data point

internal resistance = 0.60 Ω

For MP1 – do not award if only \(R = \frac{V}{I}\) is used.

For MP2 points at least 1A apart must be used.

For MP3 accept final answers in the range of 0.55 Ω to 0.65 Ω.

[3 marks]

b.

a non-zero reading when a zero reading is expected/no current is flowing
OR
a calibration error

 

OWTTE
Do not accept just “systematic error”.

[1 mark]

c.i.

the error causes «all» measurements to be high/different/incorrect

effect on calculations/gradient will cancel out
OR
effect is that value for r is unchanged

Award [1 max] for statement of “no effect” without valid argument.

OWTTE

[2 marks]

c.ii.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.i.
[N/A]
c.ii.

Syllabus sections

Core » Topic 1: Measurements and uncertainties » 1.2 – Uncertainties and errors
Show 83 related questions

View options