P2 Revision Booklet

Circuits

Easy (Grade D/E)

Q1.         A student used the apparatus below to find out how the resistance of a light-dependent resistor (LDR) depends on light intensity.

The resistance of the LDR was measured directly using a multimeter.
(a)    (i)       Which one of the following is the correct circuit symbol for a LDR?
Draw a ring around your answer.

(1)

(ii)     Name one factor that will affect the intensity of the light hitting the LDR.
...............................................................................................................
...............................................................................................................
(1)

(b)     The manufacturer of the LDR provides data for the LDR in the form of a graph.

Describe how the resistance of the LDR changes when the light intensity increases from 100 lux to 300 lux.
........................................................................................................................
........................................................................................................................
........................................................................................................................
(2)

(c)     The student only obtained three results. These are given in the table.
 
Light intensity 	Resistance in kilohms	
Dark 	750	
Bright 	100	
Very bright 	1	

(i)      The student could not use the results to draw a line graph.
Why not?
...............................................................................................................
...............................................................................................................
(1)

(ii)     Do the student’s results agree with the data the manufacturer provided?
 
Draw a ring around your answer. 	YES	NO	

Give a reason for your answer.
...............................................................................................................
...............................................................................................................
...............................................................................................................
(1)

(d)     Which one of the following circuits probably includes a LDR?
Tick () one box.
 
A circuit that automatically switches outside lights on when it gets dark.		
A circuit that automatically switches central heating on and off.		
A circuit that automatically turns lights off when no one is in the room.		

(1)
(Total 7 marks)
Q2.(a)     The diagram shows the circuit that a student used to investigate how the current through a resistor depends on the potential difference across the resistor.

(i)      Each cell provides a potential difference of 1.5 volts.
What is the total potential difference provided by the four cells in the circuit?
...............................................................................................................
         Total potential difference = .................................................. volts
(1)

(ii)     The student uses the component labelled X to change the potential difference across the resistor.
What is component X?
Draw a ring around your answer.
 
light-dependent resistor	thermistor	variable resistor	

(1)

(iii)    Name a component connected in parallel with the resistor.
...............................................................................................................
(1)

(b)     The results obtained by the student have been plotted on a graph.

(i)      One of the results is anomalous.
Draw a ring around the anomalous result.
(1)

(ii)     Which one of the following is the most likely cause of the anomalous result?
Put a tick () in the box next to your answer.
 
The student misread the ammeter.		
The resistance of the resistor changed.		
The voltmeter had a zero error.		

(1)

(iii)    What was the interval between the potential difference values obtained by the student?
...............................................................................................................
...............................................................................................................
(1)

(c)     Describe the relationship between the potential difference across the resistor and the current through the resistor.
........................................................................................................................
........................................................................................................................
(1)
(Total 7 marks)
 Q3.The diagram shows an electric circuit used in a dolls’ house.
The switches are 2-way switches; this means that each switch has a connecting wire that can be in one of two positions.

(a)     (i)      With the connecting wire in each switch in the position shown in the diagram, the lamp is off. Why?
...............................................................................................................
...............................................................................................................
(1)

(ii)     When switched on, the lamp has a resistance of 18 Ω and draws a current of 0.5 A from the power supply.
Use the equation in the box to calculate the potential difference of the power supply used in the circuit.
 
potential difference    =    current    ×    resistance	

Show clearly how you work out your answer.
...............................................................................................................
...............................................................................................................
                       Potential difference = .................................................. V
(2)

(iii)    A second, identical lamp is added to the circuit. The two lamps are joined in series.
Calculate the total resistance of the two lamps.
...............................................................................................................
                            Total resistance = .................................................. Ω
(1)

(b)     This type of circuit is also used in real houses. One of the switches is at the top of the stairs, and the other switch is at the bottom of the stairs.
What is the advantage of using this circuit to switch a lamp on or off, rather than using a more simple circuit that has only one switch?
........................................................................................................................
........................................................................................................................
(1)

(c)     The diagram shows an old type of metal lamp fitting.

The cable has been connected to the lamp fitting in a way that makes the lamp fitting unsafe.
(i)      What is the possible risk to someone touching the lamp fitting while the lamp is switched on?
...............................................................................................................
...............................................................................................................
(1)

(ii)     What should be done to make this lamp fitting safe to use?
...............................................................................................................
...............................................................................................................
(1)
(Total 7 marks)
 Q4.          (a)     The lamps in the circuits drawn below are all identical.
Each of the cells has a potential difference of 1.5 volts.

(i)      What is the potential difference across the 3 cells that are joined in series?
...............................................................................................................
                      Potential difference = .................................................. V
(1)

(ii)     What will be the reading on the voltmeter labelled V3?
                   Voltmeter reading V3 = .................................................. V
(1)

(iii)    Which voltmeter, V1, V2 or V3, will give the highest reading?
Draw a ring around your answer.
 
V1	V2	V3	

(1)

(b)     The diagram below shows a simple circuit.

(i)      Calculate the total resistance of the two resistors in the circuit.
...............................................................................................................
                           Total resistance = .................................................. Ω
(1)

(ii)     Use the equation in the box to calculate the reading on the voltmeter.
 
potential difference    =    current    ×    resistance	

Show clearly how you work out your answer.
...............................................................................................................
...............................................................................................................
                         Voltmeter reading = .................................................. V
(2)

(iii)    The current through a resistor at constant temperature changes when the potential difference across the resistor changes.
Which one of the graphs, X, Y or Z, shows how the current changes?
Write your answer, X, Y or Z, in the box.

 
    X	
 
         Y	
 
             Z	

Graph		

(1)
(Total 7 marks)
 Q5.          A circuit diagram is shown below.

(a)     Use a word from the box to label component X.
 
fuse	switch	thermistor	

(1)

(b)     Calculate the total resistance of the two resistors in the circuit.
........................................................................................................................
                                      Total resistance = ........................................ Ω
(1)

(c)     The reading on the ammeter is 0.25 A.
The current through the 6 Ω resistor will be:
 
bigger than 0.25 A	equal to 0.25 A	smaller than 0.25 A	

Draw a ring around your answer
(1)

(d)     The 6 V battery is made by correctly joining several 1.5 V cells in series.
Calculate the number of cells needed to make the battery.
........................................................................................................................
                                      Number of cells = ...........................................
(1)
(Total 4 marks)
 Q6.          The diagram shows a simple circuit.

(a)     The circuit includes an LDR.
What do the letters LDR stand for?
Draw a ring around your answer.
 
Light-dependable resistor	light-dependent resistor	light-direct resistor	

(1)

(b)     The graph shows how the resistance of an LDR changes with light intensity.

Describe in detail how the resistance of the LDR changes as the light intensity increases from 0 to 50 lux.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(3)

(c)     (i)     Complete the following sentence by drawing a ring around the correct line in the box.
 
 	decrease	 	
A decrease in the light intensity of light on the LDR will	not change	the 	
reading on the ammeter.	increase	 	

(1)

(ii)     Give a reason for your answer to part (c)(i).
...............................................................................................................
...............................................................................................................
(1)

(d)     An LDR can be used to switch a circuit on and off automatically.
In which one of the following would an LDR be used?
Put a tick () in the box next to your answer.
 
a circuit to switch on central heating when it gets cold		
a circuit to switch on security lighting when it gets dark		
a circuit to switch on a water sprinkler when the soil in a greenhouse is dry		

(1)
(Total 7 marks)
Q7.Complete each of the following sentences, A, B, C, D and E, by choosing the correct ending from K, L, M, N or O.
The first one has been done for you.
 
A	The current through a resistor depends ............................................................		
B	A direct current .................................................................................................		
C	In a series circuit, the potential difference ........................................................		
D	An alternating current .......................................................................................		
E	In a parallel circuit, the potential difference ......................................................		

K    .......................................................................... across each component is the same.
L     .................................................................................... is supplied by a cell or battery.
M    ................................................................................. is constantly changing direction.
N     ..................................................... of the power supply is shared by the components.
O    ............................................................ on the potential difference across the resistor.
(Total 3 marks)
 Q8.          Use words from the box to label the components, A, B, and C, in the circuit diagram.
 
cell          diode          lamp           resistor         switch	

(Total 3 marks)
 
Q9.          A student used the apparatus below to find out how the resistance of a thermistor changes with temperature.

The student heated the water slowly using a Bunsen burner.
The resistance of the thermistor was measured using an ohmmeter.
(a)     (i)      Before doing the experiment the student completed a risk assessment.
Which one of the following is a hazard in this experiment?
Tick () one box.
 
Using an ohmmeter near water		
Boiling water in a beaker		
Hanging the thermistor in water		

(1)

(ii)     The student measured the water temperature using a temperature probe and data logger rather than a glass thermometer.
          
Give two reasons for using a temperature probe and data logger rather than a glass thermometer to measure temperature.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)

(b)     The data obtained by the student is displayed in the graph.

What conclusions should the student make from the data displayed in the graph?
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(3)

(c)     In which one of the following circuits is there likely to be a thermistor?
Tick () one box.
 
One that automatically switches lights on when it gets dark		
One that automatically monitors the moisture level in soil		
One that acts as a thermostat to switch heating on and off		

(1)
(Total 7 marks)
 Q10.          (a)     The graphs, A, B and C, show how the current through a component varies with the potential difference (p.d.) across the component.
          Draw a line to link each graph to the correct component.
Draw only three lines.
                       
(2)

(b)     Each of the circuits, J, K and L, include two diodes.

          In which one of the circuits, J, K or L, would the filament lamp be on?
............................................................
(1)
(Total 3 marks)
 Circuits- Mark scheme

M1.         (a)       (i)     correct symbol ringed

1

(ii)     accept any suggestion that would change light intensity, eg:
•        torch on or off
accept power of torch
do not accept watts / wattage of torch
•        distance between torch and LDR
•        lights in room on or off
•        shadow over the LDR
1

(b)     resistance decreases
1

from 600 kΩ to 200 kΩ
accept by 400 kΩ
1

(c)     (i)      no numbers for light intensity
or
light intensity is categoric / a description / not continuous
not enough results is insufficient
1

(ii)     YES
mark is for the reason
both show that resistance increases with decreasing (light)intensity / brightness
accept they both get the same results / pattern
1

(d)     A circuit that automatically switches outside lights on when it gets dark.
1
[7]
 M2.         (a)      (i)     6
1

(ii)     variable resistor
1

(iii)    voltmeter
1

(b)     (i)      point at 3 V ringed
1

(ii)     The student misread the ammeter.
1

(iii)    1 (volt)
accept every volt
1

(c)     as one increases so does the otherordirectly proportionalorpositive correlation
accept a numerical description, eg when one doubles the other also doubles
1
[7]
 
M3.         (a)      (i)     circuit not complete
accept circuit is broken
accept switch / s are open / off
1

(ii)     9
allow 1 mark for correct substitution, ie 0.5 × 18 provided no subsequent step shown
2

(iii)    36
1

(b)     can be switched on / off from top or bottom of stairs
1

(c)     (i)      (electric) shock
accept fitting becomes live
accept answers giving a possible consequence of electric shock, eg death
1

(ii)     connect the earth wire
1
[7]
 
M4.         (a)      (i)     4.5
1

(ii)     2.25 or their (a)(i) ÷ 2 correctly calculated
1

(iii)    V2
1

(b)     (i)      30
1

(ii)     8
allow 1 mark for correct substitution
ie 0.4 × 20
allow 1 mark for answers of 4 or 12
2

(iii)    Y
1
[7]
 M5.          (a)     switch
allow answer circled in box
1

(b)     24
1

(c)     equal to 0.25 A
1

(d)     4
1
[4]
 
M6.          (a)     a light-dependent resistor
1

(b)     any three from:
•        resistance starts at 500 (kilohms)
•        (resistance) falls rapidly as intensity increases from 0
accept resistance falls
accept brightness for intensity
•        (resistance) halves between 10 and 20 lux
•        (resistance) falls slightly between 20 and 50 lux
or
•        (resistance) almost constant / levels out between 20 and 50 lux
•        at 50 lux, resistance = 10 (kilohms)
for full credit the word resistance must be used correctly at least once
an answer resistance falls as intensity increases gains 2 marks - this may be combined with one of the bullet point marks for full credit
3

(c)     (i)     decrease
1

(ii)     resistance increases 
this can score without (c)(i)
1

(d)     A circuit to switch on security lighting when it gets dark.
1
[7]
 M7.L
N
M
K
all four in the correct order
2 marks for 2 correct
1 mark for 1 correct
[3]
 
M8.          A – switch
1
B – cell
1
C – diode
1
[3]
 M9.         (a)     (i)      boiling water in a beaker
1

(ii)     any two from:
•        more precise
•        sensitive
•        accurate
2

(b)     higher the temperature, lower the resistance
1
plus additional detail
eg resistance falls fastest between 0-20°C
maximum of 2 marks, 1 for each additional correct detail
resistance falls slowest between 80-100°C
accept for 1 mark
resistance is not constant (at all temperatures)
3

(c)     one that acts as a thermostat to switch heating on and off
1
[7]
 M10.          (a)     three lines drawn correctly

allow 1 mark for 1 correct line
if more than one line goes from a graph, both are incorrect
2

(b)     J
1
[3]