Name: _______________________________________________
P2 Topic 2 – Static electricity
Foundation
Date:
Time: 30 minutes
Total marks available: 30
Total marks achieved: ______
Questions
Q1.
(a) A student charges two balloons and hangs them side by side.
ÍÍÍ
Explain why the cotton threads are not vertical.
(2)
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(b) The student rubs another balloon with a cloth.
This balloon becomes negatively charged.
(i) Complete the sentence by putting a cross (
) in the box next to your answer.
Compared to the charge gained by the balloon, the cloth gains
(1)
A a larger negative charge
B a larger positive charge
C an equal negative charge
D an equal positive charge
(ii) Explain why the balloon became negatively charged when it was rubbed with the cloth.
(2)
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(iii) The student then puts this charged balloon against a metal cabinet.
Describe what happens to the charge on the balloon where it touches the metal cabinet.
(2)
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(iv) The student charges another balloon and holds it against a wall. The charged balloon sticks to the
wall when he
lets go.
Suggest why the balloon is attracted to the wall.
(1)
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(Total for Question = 8 marks)
Q2.
(a) Vicky combs her hair with a plastic hair comb.
The comb now has a negative charge.
(i) Complete the sentence by putting a cross (
) in the box next to your answer.
The comb has a negative charge because it has
(1)
A gained electrons
B lost electrons
C gained protons
D lost protons
(ii) Vicky's hair has also become charged.
Explain how Vicky's hair has become charged.
(2)
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(iii) Vicky holds the comb over a small piece of metal foil.
The foil jumps up and sticks to the comb.
Show on the diagram where the foil is negatively charged.
(1)
(b) Vicky combs her hair with a metal comb.
Then she tries to pick up some small pieces of metal foil with the comb.
The metal comb does not pick up any pieces of metal foil.
Explain why the metal foil is not picked up by the comb.
(2)
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(c) The picture shows an electrostatic paint sprayer about to be used to paint a metal object.
When the paint particles leave the sprayer, they are negatively charged.
Explain the benefits of using this sprayer compared with one that does not charge the paint.
(6)
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(Total for Question is 12 marks)
Q3.
(a) A student ties two balloons to a support with some string.
The student rubs both balloons with a dry cloth which gives the balloons a negative charge.
The diagram shows the balloons after they were rubbed.
Use words from the box to complete the sentences.
(4)
The balloons ............................................... each other because they have the same
...............................................
The cloth is left with a ............................................... charge.
The charged particles that are transferred from the cloth to the balloons are called
...............................................
(b) The diagram shows an electrostatic insecticide spray being used on a plant. The plant is initially
uncharged.
Each droplet of spray is given a positive charge.
(i) Explain the advantages of using an electrostatic insecticide spray compared to an uncharged
insecticide spray.
(3)
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(ii) There is a current of 0.008 A in the sprayer for a time of 10 minutes.
Calculate the charge supplied to the sprayer in this time.
(3)
charge = ........................................................... C
(Total for Question = 10 marks)
Examiner's Report
Q1.
a
Most candidates correctly stated that the two balloons repelled each other. Better candidates could state
that this was because they both had the same charge. At this stage in the question the nature of the
charge had not been declared and examiners would accept 'both had positive charge' or 'both had
negative charge'. There is still some misunderstanding of the term static with answers such as 'both
balloons have static' being fairly common.
Results Plus: Examiner Comments
A good, clear answer which scored both marks.
Results Plus: Examiner Comments
This scored a mark for the idea that the balloons were pushing each other away, but
static charge is too vague for the other mark.
Results Plus: Examiner Comments
This gets a mark for writing that the balloons have the same charge but does not
actually state that the balloons repel and so did not get the other mark.
bii
At this stage in the question, candidates had been told that the balloon had a negative charge
and so answers which tried to give the balloon a positive charge could not be accepted. Those
who appreciated that electrons could be transferred usually went on to give the correct direction
from cloth to balloon: unlike candidates who thought that positive charge moved ( either 'positive
electrons' or 'protons' ). Surprisingly few candidates mentioned friction even though this is clearly
mentioned in the specifications. This would have given a mark regardless of any subsequent
errors in nature and direction of charge movement.
Results Plus: Examiner Comments
A good, clear answer which scored two marks.
biii-iv
In part iii, many candidates seemed to miss the point that the cabinet was metal and tried to
describe the balloon being attracted or repelled. Examiners were looking for responses which
described the movement of charge from balloon to cabinet. Failure to mention the nature of the
charge was not penalised but an incorrect statement that positive charge moved was not
accepted. Earthing is mentioned explicitly in the specification and candidates who correctly used
this term scored a mark. The flow of electrons in a metal is also in the specification and mention
of this scored a mark.
In part iv, examiners were looking for either correct use of the term induction or a description in
terms of charge separation at the surface of the wall. It was pleasing to see that a good many
candidates were able to give a very clear description of this process. Candidates who wrote that
the wall had a positive charge without directly specifying that this was at the surface, were given
the benefit of the doubt. Candidates who only stated that 'opposite charges attract' did not give
sufficient detail to score a mark.
Results Plus: Examiner Comments
This response easily made all of the possible mark points in the first part. The
description of electrostatic induction is good and is typical of many responses seen.
Q2.
(a) (ii)
Too few candidates mentioned friction or rubbing or that the hair would become positively
charged. More referred to electron transfer but often in the wrong direction. It was worrying that
some talked of positive electrons or of protons moving.
A common one mark response.
Results Plus: Examiner Comments
This candidate has electrons moving in the correct direction and so matches the second
mark point
One of the 26% scoring both marks.
Results Plus: Examiner Comments
This candidate has the correctc direction of transfer of electrons and states the correct
charge on the hair.
(a) (iii)
Over 60% of candidates were not awarded the mark for this question. Of these, many thought
that the whole section of foil was negatively charged or that the top was negative.
One of many incorrect responses.
Results Plus: Examiner Comments
negative charges drawn in wrong place.
(b)
Many candidates assumed that both pieces of metal had the same charge and repelled. Some
said that metal was a conductor and then often went on to say that electrons did not move
through metals or that they did not conduct static electricity. A number stated that a metal was
not a conductor.
A typically confused response.
Results Plus: Examiner Comments
Many candidates stated that the two metals would repel. Possibly some confusion with
magnets?
One of the 24% scoring one mark
Results Plus: Examiner Comments
A number of candidates scored a mark for stating that the metal comb would be
uncharged.
This response also indicates candidates' confusion.
Results Plus: Examiner Comments
Another very common incorrect response. Candidates seemed to think that if the metal
objects did not attract they must repel.
(c)
This question was answered better than 5(c). Again, there was a good range of marks gained by
candidates for this question. Most candidates made an attempt to answer it. Of those who made
an attempt, the majority of candidates included the attraction of charges in their answer, fewer
included points about the repulsion of charges. Good responses stated that the paint particles
would repel from each other and be attracted to the mirror but too many did not then compare it
to the workings of an uncharged sprayer.
No rewardable material.
Results Plus: Examiner Comments
A confused response but, not far away from scoring some marks.
A level one response that gained 2 marks.
Results Plus: Examiner Comments
A limited description containing one or two points that are not linked.
A level two answer gaining 4 marks.
Results Plus: Examiner Comments
The candidate has linked two points. the negatively charged paint is attracted to the
(induced) positive charge on the mirror.
A clear level three response awarded 6 marks.
Results Plus: Examiner Comments
The candidate links the negatively charged paint droplets repelling so they spread out
and improve coverage.
There is also a link between unlike charges attracting and finally, there is a comment
about the uncharged paint.
Q3.
(a)
The majority of students were able to show a good understanding of basic electrostatics in this
question.
Results Plus: Examiner Comments
This is one of the fully correct responses.
Results Plus: Examiner Comments
A common mistake was to state that protons are the charges that move.
Results Plus: Examiner Tip
In all common electrostatic phenomena it is negatively charged electrons that move.
(b) (i)
Candidates were asked to explain the advantages of using a charged insecticide spray over an
uncharged spray. Many candidates used the diagram to explain about repulsion between
charges of the same type and their attraction to the uncharged plant.
Results Plus: Examiner Comments
This is an example of a response scoring all 3 marks
Results Plus: Examiner Tip
Some weaker candidates thought that the spray was used to give plants an electrical
charge.
(b) (ii)
Candidates were asked to calculate the charge supplied to the sprayer using the equation
charge = current x time. The most common error was a failure to convert the time in minutes into
seconds.
Results Plus: Examiner Comments
This is an example of a candidate correctly writing down the equation to be used,
converting the time to seconds and evaluating the charge supplied to the sprayer.
Results Plus: Examiner Tip
Make use of the equations given at the front of the paper.
Results Plus: Examiner Comments
The candidate has used their own abbreviations of the equations supplied at the front of
the paper to find the correct answer.
Results Plus: Examiner Comments
This is an example of failing to convert the time to seconds. The examiner was able to
award 2 out of the 3 marks for this response.
Results Plus: Examiner Tip
It is important that you show all your working when answering calculations.
Mark Scheme
Q1.
Answer
(a)
(b)(i)
(b)(ii)
(b)(iii)
(b)(iv)
an explanation
linking: balloons
repel (1) (because)
they have like
charges (1)
D an equal
positive charge
an explanation
linking any two of
friction (between
cloth and balloon) (1)
transfer of electrons
(1)
(electrons/negative
charges move) from
cloth to balloon (1)
a description
including two from
the following:
 balloon becomes
discharged (1)
 metal /cabinet is
a conductor (1)
 electrons move
through / on to metal
/ cabinet (1)
(surface of) wall
(becomes) positively
charged /charged by
induction (1)
Acceptable
answers
balloons repulse /
push away
(from each other/to
the side) same
charge / both
positive / both
negative accept like
charges repel for 2
marks
Mark
(2)
(1)
charge/electrons
move accept
balloon gains
electrons from the
cloth for 2 marks
(2)
earthed / neutral
(negative) charge for
electrons accept
electrons move to
earth for 2 marks
(2)
charges on the wall
separate charge
closest to the surface
of the wall is
opposite to the
charge on the
(1)
balloon
Q2.
Answer
(a) (i)
(a)(ii)
A gained electrons
An explanation
linking any two of the
following Friction
(1) (Causes) hair
to lose electrons(to
the comb)
(1) Hair has an
(overall) positive
charge (1)
(a) (iii)
An indication that
negative charges
have been repelled (
by the comb)
(1)
(b)
An explanation
linking the following
points excess
charge is removed
/comb does not
become charged
/gain charge/static
electricity
(1)
it/charge moves
through the
metal/comb
(1)
*(c)
Acceptable
answers
Mark
(1)
Reject positive
electrons and
movement of positive
charge Rubbing
(hair with comb)
Electrons
transfer/move
(Ignore atoms)
Eg electrons
transfer to hair as
comb rubs hair gains
2 marks
An arrow/label
clearly indicating to
the bottom of the foil
Correct separation of
positive and negative
charges minus signs
shown less than
half-way up the foil
No credit for both
have the same
charge so repel
Accept electrons for
charge Charge is
earthed/flows (in)to
ground/off comb/into
Vicky Metal is a
conductor credit
they are both
neutral/have no
charge with 1 mark
Indicative Content
A description /
comparison/
explanation / etc
including some of
the following points
 paint particles
have the same
charge
 like charges
repel
 Particles repel
each other
 So spread out
(more)/form a (fine)
mist
 Even layers
 Improved finish
 Opposite
charge(is induced)
(2)
(1)
(2)
Mark
(6)
Level
1
0
1-2
on object
 Paint particles
are attracted to metal
object
 To parts not in
direct line of
spray/back of object
 Need not move
the sprayer to reach
back
 Takes less time
 Uses less paint/
less paint wasted.
 Uncharged paint
forms large
droplets/runs (off
object) Allow reverse
arguments for
uncharged paint
Accept an
explanation that
includes the idea
that there is
attraction between
charged and
uncharged/neutral/e
arthed objects
No rewardable content
 a limited description that contains one or
two points and possibly has a number of
inaccuracies
e.g. even layer....paint is attracted to object
OR uses less paint
 the answer communicates ideas using
simple language and uses limited scientific
terminology
 spelling, punctuation and grammar are
used with limited accuracy
2
3-4
 a simple description that links two points
 e.g. particles repel each other which
makes them spread out
OR They are attracted to the metal object
because it has the opposite charge.
 the answer communicates ideas
showing some evidence of clarity and
organisation and uses scientific terminology
appropriately
 spelling, punctuation and grammar are
used with some accuracy
3
5-6
 a detailed description that links two
points about repulsion and links two points
about attraction of charges
OR
a statement that links two points about
charged paint together with a comment
about uncharged paint.
e.g. particles have the same charge and
repel each other (which makes them spread
out to form even layers) AND they are
attracted to the metal object
OR
particles have the same charge and repel
each other but uncharged paint would form
big drops.
 the answer communicates ideas clearly
and coherently uses a range of scientific
terminology accurately
 spelling, punctuation and grammar are
used with few errors
Q3.