Physics - Level 2 Electricity and Electromagnetism
Immediately below this paragraph is a table
with links to the exam questions and answers for all three externals way back to 2013.
Focus on the exams for the last three years. Recognise the type of question e.g This is
a question about..... Know how you are going to set out your working when answering each type of question.
We use the L2 Physics externals Scipad. If you click on the resource booklet image a new
window will open that shows you the formula sheet you will have in the exams.
The topics covered in the Level 2 Electricity exam are
Static Electricity
Uniform Electric Field
Electric Field Strength
Force on a Charge in an Electric Field
Electric Potential Energy
Work Done on a Charge Moving in an Electric Field
DC Electricity
Circuits and their components
Current
Voltage
Resistors and Ohm's Law
Energy and Power
Combination Circuit Problems
Electromagnetism
Force on a current carrying conductor in a magnetic field
Force on charged particles moving in a magnetic field
Induced voltage generated across a straight conductor moving in a uniform magnetic field
Static Electricity
Static electricity examines what happens when charges, positive or negative, collect on a surface that
does not conduct electricity.
There is a useful
3 minute video here
unlike charges attract
like charges repel
Uniform Electric Field
This is discussed on pp239-240 of the Scipad
Field lines are drawn in the direction that a positively charged particle would move
The closer the field lines are to each other the stronger the electric field
Field lines do not intersect
Q1b from the 2023 exam
1b. On the diagram above, draw the electric field lines to represent the field between the plates.
For Achieved - At least two downward arrows between the plates
For Merit
Evenly spaced parallel field lines downwards, AND
Curved lines at the ends, AND
Lines meet the plates at right angles.
Electric Field Strength
Electric field strength is discussed on pages 241-242 of Scipad
The strength of an electric field between two parallel plates depends on the voltage between the plates
and the distance between the plates
E = V/d units are V m-1
Q1a from the 2023 exam
E = V/d = 12/0.05 = 240 V m-1
Force on a Charge in an Electric Field
Electric field strength is discussed on pages 243-246 of Scipad
F = Eq, units are Newtons, N
Q1c from the 2023 exam
1c. Use physics principles to explain how the electric force on an electron would vary as it moved
from the negative plate to the positive plate.
Answer: The electric field between the plates is uniform. F = Eq, so the force on the
electron is constant / unchanging / the same everywhere.
For Achieved - mention uniform E or constant F
For Merit - Uniform E and Constant F
Electrostatic Potential Energy
Electrostatic Potential Energy is discussed on pages 243-250 of Scipad
ΔEp = Eqd
The change in potential energy is negative if the charge is moving towards an opposite charge
(potential energy is converted to kinetic energy)
The change in potential energy is positive if the charge is being forced toward a like charge
(potential energy is increased by the work done)
Q1d from the 2023 exam
1di. Calculate the change in electric potential energy as the electron moves from point A to
point B on the diagram
Ep = Eqd = 240*1.6 x 10 -19*0.05 = 1.92 x 10-18 J
There is no change in Ep as there has been no change in 'd'
Achieved if one of the Ep is correct. Merit if both are correct.
1d(iii) Use physics principles to explain any difference in the change in electrical potential
energies found in parts (i) and (ii).
In (i) the electron is moving along the field lines, so there is a change in
voltage, and a change in electric potential energy. OR there is a force in
the direction of movement, so work is done OR it’s getting closer (further
away) from the positive / negative plate
In (ii) the electron is moving across the field lines, so there is no change in
voltage, and no change in electric potential energy. OR there is no force
on the electron in the direction of its movement, so no work is done. OR
the distance from the plates does not change.
For 'Excellence' you need the two Ep correct and an explanation
Work Done on a Charge Moving in an Electric Field
DC Electricity
Current
An electric current is produced when electrons flow from the negative terminal to the positive
terminal of a battery. Each electron has a very small negative charge. A current, I, of 1 Ampere is
produced when 1 Coulomb (6.24 x 1018) of electrons passes a point in one second
I = Q/t
Voltage
When a bulb is connected to a battery it gives off heat and light, two forms of energy. The source of
that energy, as well as the source of the electrons which travel around the circuit is the battery.
V = ΔE/q
Voltage is measured by a voltmeter connected in parallel between two points in a circuit. For example
a voltmeter connected to the positive and negative terminals of a battery will record the voltage of the battery.
In a series circuit the voltage is divided among the components/
Each arm of a parallel circuit receives the same voltage.
There are two formulas for power. The units of Power are Watts (W)
P = ΔE/t
P = VI
Bulbs convert electrical energy to light and heat energy. The brightness of a lamp depends on the rate
at which it uses energy i.e its power consumption, or VI
Combination Circuit Problems
In a 'series' circuit
Current is the same at all points on the circuit.
Voltage is shared among the components of a circuit.
Resistance RTot = 1/R1 + 1/R2 + 1/R3
In a parallel circuit
Current Will be different along paths if the resistances along the paths are different. The
current entering a parallel block is equal to the current leaving a parallel block.
Voltage is the same along each branch
Resistance 1/RTot = 1/R1 + 1/R2 + 1/R3
Q1a from the 2021 exam
I = V/R = 8/12 = 0.667A
Q1b from the 2021 exam
Q1c from the 2021 exam
Q1d from the 2021 exam
Electromagnetism
A magnetic field is produced whenever an electric charge is in motion.
The unit of magnetic field strength is the Tesla. 'B' is the symbol for magnetic field strength.
There is a useful
5 minute video here. The 'right hand' rule is important. You should also know what a solenoid is.
There is another useful
5 minute video here. It is important that you understand how an electric motor works. Remember we use the right hand rule.
Force on a current carrying conductor in a magnetic field
Q3a from the 2023 exam
Answer 3a. Arrow to left (Achieved)
Answer 3b. F = BIL, need to find current
I = V/R = 120/42.1 = 2.85A (Achieved)
F = BIL = 8.1 x 10-3 x 2.85 x 0.84 = 0.0194N (Merit)
Force on charged particles moving in a magnetic field
Q3d from the 2022 exam
Answer 3d(i) The direction is anti-clockwise
Answer 3d(ii) The moving electron produces a magnetic field.
This magnetic field adds / combines / interacts with the
magnetic field that the electron is moving through,
making a weaker field on one side, and a stronger field
on the other side of the path of travel.
The electron experiences a force towards the weaker
side.
Induced voltage generated across a straight conductor moving in a uniform magnetic field
Q3c from the 2023 exam
Answer 3c(i). Top end labelled negative
3c(ii). V = BvL = 8.1 x 10-3 x 3.1 x 0.95 = 0.0239V
Q3d from the 2023 exam
Describe the motion of the axle after it is set moving. Justify your answer using electromagnetism physics principles
After the axle is set moving, a voltage is induced between the ends. As
there is a complete circuit a current is induced in the axle. The axle is now
a current carrying conductor cutting a magnetic field, so there is a force on
the axle. This force opposes the motion, and the axle slows down.
Voltage induced
Complete circuit/induced current
current carrying wire in magnetic field
Force opposing motion
slows down
For Achieved, describes 2 effects, 3 for merit, all 5 for excellence
