Madeley High School
Current electricity exam qs C grade
Q1.(a)
The diagram shows a negatively charged plastic rod held near to a thin stream of water. The
water is attracted towards the rod.
Which one of the following statements explains what is happening to the charge in
the water?
Tick (
) one box.
The positive and the negative charges in the water are
attracted to the rod.
The positive and the negative charges in the water are
repelled by the rod.
The negative charge in the water is repelled by the rod and
the positive charge is attracted to the rod.
The negative charge in the water is attracted to the rod and
the positive charge is repelled by the rod.
(1)
(b)
A company that produces bottles of mouthwash found a problem with the automatic
filling system.
As the bottles go towards the filler, the bottles move around on the conveyor belt
and become electrostatically charged. This causes the stream of mouthwash to
move sideways, missing the open top of the bottle.
Page 1
Madeley High School
The company came up with an answer to the problem. Before the bottles reach the
dfiller, the bottles pass through a stream of ionised air. The ions in the air neutralise
the charge on the bottles.
(i)
Explain why the plastic bottles became charged.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(ii)
What happens to the structure of an atom to change the atom into an ion?
...............................................................................................................
...............................................................................................................
(1)
(iii)
Earthing the conveyor belt with a conducting wire would not have solved this
problem.
Give a reason why.
...............................................................................................................
...............................................................................................................
(1)
(Total 5 marks)
Page 2
Madeley High School
Q2.
(a) The diagram shows the voltage-current graphs for three different electrical
components.
Which one of the components A, B or C could be a 3 volt filament lamp? Explain
the reason for your choice.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(b)
Using the correct symbols draw a circuit diagram to show how a battery, ammeter
and voltmeter can be used to find the resistance of the wire shown.
(3)
(c)
When correctly connected to a 9 volt battery the wire has a current of 0.30 amperes
flowing through it.
(i)
Give the equation that links current, resistance and voltage.
..........................................................................................................................
(1)
Page 3
Madeley High School
(ii)
Calculate the resistance of the wire. Show clearly how you work out your
answer and give the unit.
..........................................................................................................................
..........................................................................................................................
Resistance = .........................................................
(3)
(iii)
When the wire is heated, the current goes down to 0.26 amperes. State how
the resistance of the wire has changed.
...........................................................................................................................
...........................................................................................................................
(1)
(Total 11 marks)
Q3.(a)
The diagram shows the circuit used to investigate the resistance of a sample of a material.
The diagram is not complete; the ammeter and voltmeter are missing.
(i)
Draw the symbols for the ammeter and voltmeter on the diagram in the correct
places.
(2)
(ii)
How can the current through the material be changed?
...............................................................................................................
...............................................................................................................
(1)
Page 4
Madeley High School
(b)
The material, called conducting putty, is rolled into cylinders of different lengths but
with equal thickness.
Graph 1 shows how the resistance changes with length.
Length in centimetres
(i)
The current through a 25 cm length of conducting putty was 0.15 A.
Use Graph 1 to find the resistance of a 25 cm length of conducting putty.
Resistance = .................................................. ohms
(1)
(ii)
Use your answer to (b) (i) and the equation in the box to calculate the potential
difference across a 25 cm length of conducting putty.
potential difference = current x resistance
Show clearly how you work out your answer.
...............................................................................................................
...............................................................................................................
...............................................................................................................
Potential difference = .................................................. volts
(2)
Page 5
Madeley High School
(c)
A second set of data was obtained using thicker pieces of conducting putty. Both
sets of results are shown in Graph 2.
Length in centimetres
(i)
What is the relationship between the resistance and the thickness of the
conducting putty?
...............................................................................................................
...............................................................................................................
(1)
(ii)
Name one error that may have reduced the accuracy of the results.
...............................................................................................................
(1)
(iii)
How could the reliability of the data have been improved?
...............................................................................................................
...............................................................................................................
(1)
(Total 9 marks)
Page 6
Madeley High School
Q4.
(a)
(i)
The circuit diagram drawn below includes a component labelled X.
Use the equation in the box to calculate the potential difference across the
8 ohm resistor.
potential difference = current × resistance
Show clearly how you work out your answer.
..........................................................................................................................
..........................................................................................................................
Potential difference = ................................................. volts
(2)
(ii)
What is the potential difference across component X?
..........................................................................................................................
(1)
(b)
The graph shows how the resistance of component X changes with temperature.
(i)
What is component X?
.....................................................
Page 7
(1)
Madeley High School
(ii)
Over which range of temperatures does the resistance of component X
change the most?
Put a tick ( ) next to your choice.
0 °C to 20 °C
20 °C to 40 °C
40 °C to 60 °C
60 °C to 80 °C
80 °C to 100 °C
(1)
(Total 5 marks)
Q5.
The current through component X is measured when different voltages are applied
across it.
(a)
Name the component labelled Y in the circuit.
.....................................................................................................................................
(1)
(b)
What type of meter is Z?
.....................................................................................................................................
(1)
Page 8
Madeley High School
(c)
The table shows the measurements obtained in this experiment.
Voltage in V
0
0.2
0.4
0.6
0.8
Current in mA
0
0
50
100
150
Draw a graph of the measurements.
(2)
(d)
Use the shape of the graph to name component X.
.....................................................................................................................................
(1)
(Total 5 marks)
Page 9
Madeley High School
Q6.
The drawing shows the circuit used to investigate how the current through a 5 ohm
(Ω) resistor changes as the potential difference (voltage) across the resistor changes.
(a)
Draw, in the space below, a circuit diagram of this circuit. Use the correct symbols
for each part of the circuit.
(2)
(b)
(i)
Write down the equation that links current, potential difference and resistance.
...........................................................................................................................
(1)
Page 10
Madeley High School
(ii)
Calculate the potential difference across the 5 ohm (Ω) resistor when the
current through the resistor equals 0.4 A. Show clearly how you work out your
final answer.
...........................................................................................................................
...........................................................................................................................
potential difference = .............................................. volts
(2)
(iii)
Complete the graph to show how the current through the resistor changes as
the potential difference across the resistor increases from 0 V to 3 V. Assume
the resistor stays at a constant temperature.
(2)
(c)
The resistor is replaced by a 3 V filament lamp. The resistance of the lamp
increases as the potential difference across it increases. Why?
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 8 marks)
Page 11
Madeley High School
Q7.The diagram shows the circuit set up by a student.
(a)
The student uses the circuit to test the following hypothesis:
‘The current through a resistor is directly proportional to the potential
difference across the resistor.’
(i)
If the hypothesis is correct, what should the student predict will happen to the
current through the resistor when the potential difference across the resistor is
doubled?
...............................................................................................................
...............................................................................................................
(1)
(ii)
Name the component in the circuit used to change the potential difference
across the resistor.
...............................................................................................................
(1)
(b)
The student used the data obtained to plot the points for a graph of current against
potential difference.
Page 12
Madeley High School
(i)
Why has the student plotted the points for a line graph and not drawn a bar
chart?
...............................................................................................................
...............................................................................................................
(1)
(ii)
One of the points has been identified by the student as being anomalous.
What is the most likely cause for this anomalous point?
...............................................................................................................
...............................................................................................................
(1)
(iii)
Draw a line of best fit for these points.
(1)
(iv)
Does the data the student obtained support the hypothesis?
Give a reason for your answer.
...............................................................................................................
...............................................................................................................
(1)
(Total 6 marks)
Page 13
Madeley High School
Q8.
A student designed the circuit below to measure temperature using a thermistor.
To calibrate the thermistor to measure temperature, the student placed the thermistor in a
beaker of water at 0 °C and took the voltmeter reading. The student then heated the water
slowly with a Bunsen burner. The student recorded the reading on the voltmeter every 10
°C.
(a)
(i)
Before calibrating the thermistor the student completed a risk assessment.
Write down one possible hazard that the student should have written in the
risk assessment and what the student should do to reduce the risk of the
hazard causing an injury.
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)
(ii)
At 0 °C the reading on the ammeter is 0.5 A.
Calculate the reading on the voltmeter at 0 °C.
Write down the equation you use, and then show clearly how you work out
your answer.
...............................................................................................................
...............................................................................................................
...............................................................................................................
Voltmeter reading = ..................................... V
Page 14
Madeley High School
(2)
(b)
Most of the readings taken by the student are displayed in the graph.
(i)
Explain why the reading on the voltmeter changes when the temperature of
the water increases.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(3)
(ii)
What is the temperature interval that can be measured with this circuit?
...............................................................................................................
Page 15
Madeley High School
...............................................................................................................
(1)
(iii)
Once calibrated, between which temperatures would this circuit give the
greatest resolution for temperature readings?
Tick ( ) one box.
20 °C to 40 °C
40 °C to 60 °C
60 °C to 80 °C
Give a reason for your answer.
...............................................................................................................
...............................................................................................................
(2)
(c)
Thermistors have many practical uses, including being used as a thermometer to
measure temperature.
Give one other practical use for a thermistor.
........................................................................................................................
........................................................................................................................
(1)
(Total 11 marks)
Page 16
Madeley High School
Current electricity exam qs C grade
M1.(a)
3rd box
The negative charge in the water is repelled by the rod and the positive charge is attracted
to the rod.
1
(b)
(i)
friction between bottles and conveyor belt / (plastic) guides
accept bottles rub against conveyor belt / (plastic) guides
1
charge transfers between bottles and conveyor belt / (plastic) guides
accept specific reference eg electrons move onto / off the
bottles
reference to positive electrons / protons negates this mark
1
(ii)
(the atom) loses or gains one (or more) electrons
1
(iii)
charge will not (easily) flow off the conveyor belt / bottles
accept the conveyor belt / bottles is an insulator / not a
conductor accept conveyor belt is rubber
1
[5]
M2.
(a)
C
award mark if A and B identified as not filament lamp
1
resistance increases
negated by wrong statement e.g. current goes down
1
as the lamp gets hot
accept as current (through lamp) or voltage (across lamp)
increases
do not accept non-ohmic reason independent of choice of
Page 17
Madeley High School
component
1
(b)
ammeter wire and battery only in series
non standard symbols acceptable if correctly identified
(labelled) for ammeter, voltmeter and battery
1
voltmeter only in parallel with wire or battery
all in series or ammeter in parallel neither of these two
marks awarded
1
all symbols correct
ignore lines drawn through centres of symbols
1
(c)
(i)
voltage = current × resistance
accept V = I × R
accept volts = amps × ohms
do not accept V = C × R
accept
if subsequent method correct
1
(ii)
30
accept correct substitution for 1 mark (9/0.3)
2
ohms
accept correct symbol Ω
1
(iii)
goes up
must be a comparison
accept calculation if answer is larger than c (ii)
1
[11]
Page 18
Madeley High School
M3.(a)
(i)
ammeter symbol correct and drawn in series
accept
do not accept lower case a
1
voltmeter symbol correct and drawn in parallel with the material
do not accept
1
(ii)
adjust / use the variable resistor
accept change the resistance
orchange the number of cells
accept battery for cell
accept change the pd / accept change the voltage
accept increase / decrease for change
1
(b)
(i)
37.5 (Ω)
accept answer between 36 and 39 inclusive
1
(ii)
5.6(25) or their (b)(i) × 0.15
allow 1 mark for correct substitution ie 37.5 or their (b)(i) ×
0.15 provided no subsequent step shown
2
(c)
(i)
the thicker the putty the lower the resistance
answer must be comparativeaccept the converse
1
Page 19
Madeley High School
(ii)
any one from:
•
measuring length incorrectly
accept may be different length
•
measuring current incorrectly
do not accept different currents
•
measuring voltage incorrectly
do not accept different voltage
•
ammeter / voltmeter incorrectly calibrated
•
thickness of putty not uniform
do not accept pieces of putty not the same unless qualified
•
meter has a zero error
do not accept systematic / random error
accept any sensible source of error eg putty at different
temperatures
do not accept human error without an explanation
do not accept amount of putty not same
1
(iii)
repeat readings and take a mean
accept check results againaccept do experiment againaccept
do it again and take mean(s)
accept compare own results with other groups
do not accept take more readings
1
[9]
M4.
(a)
(i)
4 (V)
allow 1 mark for correct substitution
2
(ii)
5 (V) or (9 – their (a)(i)) correctly calculated
e.c.f
do not allow a negative answer
1
(b)
(i)
thermistor
c.a.o
1
(ii)
0°C to 20°C
1
[5]
Page 20
Madeley High School
M5.
(a)
variable resistor
accept rheostat
1
(b)
voltmeter
1
(c)
straight line correct between 0.2 and 0.8
if line incorrect, or no line, and correct plots 0.2 to 0.8 award
1 mark
2
(d)
diode / rectifier
1
[5]
M6.
(a)
all symbols correct
accept push switch symbol switch may be open or closed
any lines through symbols = 0 marks
1
correct circuit drawn
polarity of cells not relevant provided they are joined
correctly
1
voltmeter must be across resistor only
two cells are required in the diagram
ignore the order of the components
allow small gaps in circuit
omission of any component = 0 marks
1
Page 21
Madeley High School
(b)
(i)
potential difference = current × resistance
accept voltage or p.d. for potential difference
accept V= I × R
accept
provided I R subsequent use correct
do not accept C for current
1
(ii)
2
allow 1 mark for correct substitution
wrong working loses both marks
2
(iii)
straight line drawn through the origin
judge by eye
straight line passes through I = 0.4, V = their (b)(ii) / 2 and 0.0
this mark may be awarded if all points shown including these
points are correct even if no line is drawn
N.B. a curve scores 0 marks
1
(c)
temperature increases
accept filament lamp / it gets hotter
allow heat for temperature
1
[8]
M7.
(a)
(i)
also double
increases is insufficient
1
(ii)
variable resistor
accept rheostat / potentiometer
1
Page 22
Madeley High School
(b)
(i)
the data / results / variables are continuous
accept data / results / variables are not categoric / discrete
1
(ii)
misreading the ammeter
do not accept misreading the meter / results
do not accept misreading the ammeter and / or voltmeter
reading / human error is insufficient
1
(iii)
straight line from the origin drawn passing close / through
points at 1 V, 5 V, 6 V and ignoring anomalous point
do not accept line drawn ‘dot-to-dot’
1
(iv)
yes
mark is for the reason
supports predictionor(straight) line passes through the origin
accept a mathematical argument, eg when p.d. went from 2
to 4 the current went from 0.3 to 0.6
it’s directly proportional is insufficient
1
[6]
M8.
(a)
(i)
spilling boiling / hot water
accept any sensible suggestion
1
suitable precaution to reduce risk from hot water eg
clamp the probe / complete the experiment standing
accept any sensible answer but must be linked to the named
risk
1
(ii)
3 (V)
allow 1 mark for substitution into correct equation
Page 23
Madeley High School
ie 0.5 × 6
2
(b)
(i)
resistance of thermistor decreases
1
therefore the current in the circuit increases
1
causing a bigger share of the p.d. across 6 Ω resistor
1
(ii)
0 – 100 (°C)
accept 10° – 100°C
1
(iii)
20°C to 40 °C
1
because a small temperature change gives a bigger
voltmeter reading change
1
(c)
thermostat
accept a correct description of a use
1
[11]
Page 24