Download 19 Omission Where a candidate response is incomplete, marks

19 Omission
Where a candidate response is incomplete, marks should be awarded for relevant points
that are included.
Example/comment
Questions requiring candidates to give
an explanation. Marking scheme
indicates four points are required each
worth ½ mark.
Candidates response includes up to
three correct points.
Candidates could achieve ½, 1, 1½.
Marking symbol
Inverted V where
information is omitted
Question:
Use the kinetic model to explain what
happens to the pressure of the trapped
air as its volume decreases. Assume
its temperature remains constant.
Marking scheme gives four ½ marks;
More frequent collisions ½
with the wall ½
greater force ½
greater pressure ½
Response:
“More frequent collisions with the
walls cause a greater pressure.”
Award 1½/2
more frequent collisions with the
walls cause a greater pressure.
^
Inverted V
Where
information
is omitted.
Credit should be given where the omitted information can be readily inferred from the
response.
Question:
Calculate the current in a 20 Ω resistor
when voltage of 5 V is supplied.
Response:
“I = 5/20 = 0.4”
In this case the candidate has used the
correct formula but has omitted to
write down the formula.
Award ½ mark for the formula, ½ mark
for correct substitution into implied formula.
I = 5/20 = 0.4 Tick beside substitution
Straight line through
final answer
Example/comment
Question:
Candidate is asked to find number of lines per metre
on the grating.
Marking schedule allows three marks.
First fringe
37°
Central fringe
nλ = d sin θ (1/2)
1 x 633 x 10 − 11 = d sin 37 (1/2) for λ, (1/2) for n
d = 1.05 x 10 − 6 (1/2)
lines/m
= 1.05 x 10 5 (1)
Response:
633x 10
−9
= d sin 37
^
This gets (11/2) marks
½ for implied formula
½ for correct n
½ for λ
Candidates must answer the question posed correctly before the marks can be awarded for an
explanation. A correct explanation or justification without the correct answer or no answer is
awarded 0 marks, if the question states candidates must justify their answer.
Example/comment
Question:
Candidate is asked to explain what happens to the reading
on a voltmeter connected across battery with internal
resistance when a second resistor is added in parallel.
Response:
Increase (1/2)
Resistance in circuit less (1/2)
Current increases (1/2)
Lost volts increases (1/2)
Award (2) marks
Response:
Resistance in circuit less
Current increases
Lost volts increases
Award (0) marks
Inverted V
Where information is omitted