P1 Revision Booklet

Electromagnetic Induction

Easy (Grade D/E)

Q1.(a)     The diagram shows a simple transformer made by a student. The student has designed the transformer to light a 3.0 V lamp using a 1.0 V power supply.

(i)      What name is given to the part of the transformer that is made of iron?
Draw a ring around your answer.
 
centre	connector	core	

(1)

(ii)     When the power supply is switched on, the lamp is not very bright.
Suggest one change that the student can make to increase the brightness of the lamp.
The 1.0 V power supply cannot be changed.
...............................................................................................................
...............................................................................................................
(1)

(b)     The diagram shows part of the National Grid system. The transformers, J, K, L and M, are an essential part of the system.

(i)      Which transformer, J, K, L or M, is a step-up transformer?
 
Write your answer in the box.		

(1)

(ii)     Some scientists claim to have found evidence to suggest that children living near to overhead power lines are more likely to develop leukaemia. However, the scientists are not sure that the power lines are the cause of the problem.
The evidence from this and other investigations may worry some people.
What do you think scientists should do?
Put a tick () in the box next to your answer.
 
Scientists should always publish the evidence from investigations immediately.		
Scientists should ignore any evidence from investigations that may worry people.		
Scientists should publish the evidence from an investigation only when they
have found out as many facts as possible.		

(1)
(Total 4 marks)
 Q2.          A student investigates the electromagnetic force acting on a wire which carries an electric current. The wire is in a magnetic field.
The diagram shows the circuit which the student uses.
(a)     Draw an X on the diagram, with the centre of the X in the most strongest part of the magnetic field.

(1)

(b)     Give one change that she can make to the magnets to decrease the electromagnetic force on the wire.
........................................................................................................................
........................................................................................................................
(1)

(c)     The student wants to change the electromagnetic force on the wire without changing the magnets or moving their position.
(i)      Give one way in which she can increase the electromagnetic force.
...............................................................................................................
...............................................................................................................
(1)

(ii)     Give one way in which she can reverse the direction of the electromagnetic force.
...............................................................................................................
...............................................................................................................
(1)
(Total 4 marks)

 
Q3.         The diagram shows a transformer made by a student. The student has designed the transformer to make a 6 V light bulb work using a 2 V power supply.

(a)     Draw a ring around the correct answer to complete the following sentences.
 
(i)     For the transformer to work, the student	must use an a.c.
can use either an a.c or a d.c.
must use a d.c.	

power supply.
(1)

(ii)     On the primary coil there are 30 turns of wire. For the lamp to work brightly
 
 	less than 30
exactly 30
more than 30	 	
there must be		turns of wire on the secondary coil.	

(1)

(b)     What is the transformer core made from?
Give a reason for your answer.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(2)
(Total 4 marks)
 Q4.          Electricity is generated in power stations. It is then sent to all parts of the country through a network of cables.
(a)           Complete the following sentence by using one of the words in the box.
 
                Grid                      Power                  Supply	

The network is called the National ............................................................................ .
(1)

(b)     In the diagram, A, B, C and D are transformers.

(i)      Which transformer, A, B, C or D, is a step-up transformer?
         Transformer ..............................
(1)

(ii)     Which transformer, A, B, C or D, will supply homes, offices and shops?
         Transformer ..............................
(1)

(c)     Complete the following sentence by drawing a ring around the correct line in the box.
          In a step-down transformer, the potential difference (p.d.) across the
 
 	less than	 	
primary coil is	the same as	the p.d. across the secondary coil.	
 	more than	 	

(1)
(Total 4 marks)
Q5.          (a)     Complete the description of the device shown below by drawing a ring around the correct line in each box.

 	 	an electric motor.	
(i)	The device is being used as	a generator.	
 	 	a transformer.	

(1)

(ii)     The coil needs a flick to get started. Then one side of the coil is pushed by the
 
cell	 	
coil	and the other side is pulled, so that the coil spins.	
force	 	

(1)

(b)     Suggest two changes to the device, each one of which would make the coil spin faster.
1 ......................................................................................................................
........................................................................................................................
2 ......................................................................................................................
........................................................................................................................
(2)

(c)     Suggest two changes to the device, each one of which would make the coil spin in the opposite direction.
1 ......................................................................................................................
........................................................................................................................
2 ......................................................................................................................
........................................................................................................................
(2)
(Total 6 marks)
 Q6.          When a conductor carrying an electric current is placed in a magnetic field a force may act on it.

(a)     State two ways in which this force can be increased.
1 ..................................................................................................................................
2 ..................................................................................................................................
(2)

(b)     State two ways in which this force can be made to act in the opposite direction.
1 ..................................................................................................................................
2 ..................................................................................................................................
(2)

(c)     In what circumstance will no force act on a conductor carrying an electric current and in a magnetic field?
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 5 marks)

Show clearly how you work out your answer.
.....................................................................................................................................
.....................................................................................................................................
Kinetic energy = ............................................... J
(2)
(Total 7 marks)
 Electromagnetic Induction-Mark scheme
M1.         (a)      (i)     core
1

(ii)     increase number of turns on secondary (coil)
do not accept coils for turns
orreduce number of turns on primary (coil)
1

(b)     (i)      J
1

(ii)     Scientists should publish the evidence from an investigation only
when they have found out as many facts as possible
1
[4]
 M2.          (a)     centre of the X midway between the poles
intention correct as judged by eyeexample

1

(b)     move the poles further apart
accept turn for move
accept ends / magnets for poles
accept use weaker magnets
do not accept use smaller magnets
1

(c)     (i)     add more cells (to the battery)
do not accept ‘use a bigger battery’
accept increase the potential difference / voltage
accept increase the current
orreduce the resistance (of the variable resistor)
do not accept any changes to the magnets, to the wire or to their relative positions
1

(ii)     reverse (the polarity of) the battery
accept turn the battery / cells round
accept swap the connections to the battery
do not accept any changes to the magnets, to the wire or to their relative positions
1
[4]
 M3.          (a)     (i)      must use an a.c.
1
(ii)     more than 30
1

(b)     iron
reason can only score if iron is chosen
1
because it can be magnetised (and demagnetised) easily
1
[4]
M4.          (a)     grid
accept any unambiguous indication
1
(b)     (i)      A (only)
1
(ii)     D (only)
1
(c)     more than
accept any unambiguous indication
1
[4]
 M5.         (a)      (i)     an electric motor
1

(ii)     force
1

(b)     any two from:
•        more powerful magnet
do not allow ‘bigger magnet’
•        reduce the gap (between magnet and coil)
•        increase the area of the coil
•        more powerful cell
do not allow ‘bigger cellߣ
accept battery for cell
accept add a cell
accept increase current / potential difference
•        more turns (on the coil)
allow ‘more coils on the coilߣ
do not allow ‘bigger coilߣ
2

(c)     reverse the (polarity) of the cell
allow ‘turn the cell the other way round’
accept battery for cell
1

reverse the (polarity) of the magnet
allow ‘turn the magnet the other way up’
1
[6]
 M6.          (a)     increase the current (1)
credit increase the p.d./voltage
credit reduce the resistance
credit have thicker wiring
credit add extra / more cells
1
          increase the magnetic field (strength) (1)
credit ‘have stronger magnet(s)
do not credit ‘bigger magnets’ either order
1

(b)     either reverse polarity
          or connect the battery the other way round
1
          either reverse direction of the magnetic field
          or put the magnet the other way round / reverse the magnet
do not give any credit to a response in which both are done at the same time
either order
1

(c)     either
          conductor parallel to the magnetic field
          or lines of magnetic force and path of electricity do not cross
1
[5]