Q2 · 2020 · Paper 2Complex familiar6 marks
QUESTION 2 (6 marks)
A physicist measured the electric field strength at different distances away from a point charge. The data is plotted in the graph.
a)[3 marks]
Identify the mathematical relationship between and .
b)[3 marks]
Use the mathematical relationship identified in 2a) to deduce the magnitude of the charge creating the electric field.
WORKED SOLUTION
6 marksQCAA guide · typeset solution
ANSWER
See worked solution below.
Worked solution
c = 0
m =
2000 − 0
0.0278 − 0 = 72 000
E = 72 000(
1
𝑟𝑟2)
(𝐸𝐸=
1
4𝜋𝜋𝜀𝜀0
𝑞𝑞
𝑟𝑟2 )
equate the gradient to kq.
q = 72 000 / 9 x 109 C = 8 x 10–6 C
Charge = 8.0 x 10–6 C
• provides a correct value for the y-intercept [1
mark]
• provides a correct value for the gradient of the
graph [1 mark]
• provides the equation [1 mark]
• indicates an understanding of the physical
scenario in relation to the gradient being used to
find the charge [1 mark]
• provides pertinent mathematical operations
correctly performed [1 mark]
• determines the charge [1 mark]
One QCAA sample method typeset for web; criterion wording is adapted from the official marking guide.
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