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Scheme of work – Cambridge International AS Level Physical Science (8780)
Ph5 PHYSICS
Unit 5: Electricity and magnetism
Recommended prior knowledge
Students should be aware of the two types of charge and charging by friction and by induction. They should be able to distinguish between conductors and
insulators using a simple electron model.
Context
Current electricity is an important topic in the general education of any person in this modern world. An understanding of static charge and current electricity in this
Unit is an essential prerequisite to further, more advanced studies in physics or physical science.
Outline
Students will become familiar with the basic definitions and equations used in the study of current electricity. The I-V relationships for different circuit components
are investigated. Components are then linked together so that practical circuits may be studied. Electric fields and the motion of free charged particles are also
studied as further examples of charges in motion.
Syllabus ref
Learning objectives
Suggested teaching activities
Learning resources
Candidates should be able to
There is a limited supply of past papers
for the 8780 examination, therefore all
examples of examination questions are
taken from Physics 9702 AS papers.
These reflect the type of question that
candidates are likely to meet in the
8780 examinations.
10(a)
10(b)
v1 2Y05
recall the two types of charge
recall the laws of electrostatics
Discussion and revision of basic ideas, simple demonstrations / class
experiments showing the laws of electrostatics
Cambridge International AS Level Physical Science (8780)
Polythene and acetate rods, cloth and
tissue to charge rods, means of
suspending the rods.
1
Syllabus ref
Learning objectives
Suggested teaching activities
10(c)
distinguish between conductors
and insulators using a simple
electron model
Discussion of conductors and insulators, non-metals are generally
conductors – whereas metals are conductors. Relate to simple models
from chemistry section of the syllabus.
10(d)
show an understanding of the
concept of an electric field as an
example of a field of force and
define electric field strength as
force per unit positive charge
acting on a stationary point
charge.
Discussion: what is a field of force?
electric field of force
definition of electric field strength
H.T. supply, various shapes of
electrode, olive oil, semolina, petri dish,
OHP (if available)
10(e)
represent an electric field by
means of field lines.
Discussion: representation of an electric field
– electric field lines
Demonstration: electric field lines
Examples including:
May/June 2010, 9702 Paper 21,
question 5
Oct/Nov 2007, 9702 Paper 1,
question 27
Properties of field lines including spherical charge approximating to a
point charge (Although the field shape of point charge is not formally on
the syllabus it is useful for students to be aware of this common type of
field)
10(f)
recall and use E = V/d to
calculate the field strength of the
uniform field between charged
parallel plates in terms of
potential difference and
separation.
Field due to parallel plates, mention of edge effect.
Field strength = V/d in centre region
10(g)
calculate the forces on charges in
uniform electric fields.
Discussion: force = Eq is constant for constant E
Discussion: force on particle gives rise to acceleration
10(h)
apply the effect of a uniform
electric field on the motion of
Demonstration of deflection using ‘Teltron’ displacement tube
Discussion: acceleration of electrons in a c.r.o. and the role of the x and
y-palates.
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Cambridge AS Level Physical Science (8780)
Learning resources
Examples including:
Oct/Nov 2009, 9702 Paper 12,
question 26
Oct/Nov 2009, 9702 Paper 12,
question 28
Oct/Nov 2007, 9702 Paper 1,
question 26
Examples including:
Oct/Nov 2010 9702 Paper 22
question 4
May/June 2009, 9702 Paper 21,
question 6
Oct/Nov 2008, 9702 Paper 2,
2
Syllabus ref
Learning objectives
Suggested teaching activities
Learning resources
question 4
Oct/Nov 2009, 9702 Paper 12,
question 27
May/June 2011 9702 paper 12
question 31
charged particles and apply to the
c.r.o.
12(a)
recall and use appropriate circuit
symbols as set out in the ASE
publication Signs, Symbols and
Systematics.
Discussion and revision:
– why use circuit symbols?
– symbols already met
Handout of symbols based on Signs,
Symbols and Systematics
12(b)
draw and interpret circuit
diagrams containing sources,
switches, resistors, ammeters,
voltmeters, and/or any other type
of component referred to in the
syllabus.
Drawing circuits: meaning of ‘series’ and ‘parallel’
Experiment: interpreting and setting up circuits
Circuit diagrams and corresponding
components, leads
11(a)
show an understanding that
electric current is the flow of
charged particles.
Discussion: what is electric current?
Evidence provided by (i) electrolysis
(ii) migration of ions
Direction of movement of charge
– movement of electrons in metals
– conventional current
copper voltameter, d.c. supply
h.t. supply, leads and croc clips, filter
paper, ammonia solution, potassium
permanganate crystals
Revision of base units
– unit of current (amp) is a base unit
– unit of time (second) is a base unit
11(b)
define the coulomb
11(c)
recall and solve problems using Q
= It
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Definition of charge and the coulomb in terms of base units. Q = It
Cambridge AS Level Physical Science (8780)
Examples sheet including
May/June 2011 9702 Paper 11
question 31
Oct/Nov 2009, 9702 Paper 12,
question 33
Oct/Nov 2007, 9702 Paper 1,
question 30
3
Syllabus ref
Learning objectives
Suggested teaching activities
11(d)
define potential difference and the
volt.
Discussion: charges in motion – where has the energy come from?
Potential difference (p.d.) as energy per unit charge transferred from
electrical to some other form. V = W/Q and / or as the work done per
unit charge, revision of term work.
Volt defined as joule per coulomb.
11(e)
recall and solve problems using V
= W/Q
11(g)
define resistance and the ohm.
11(h)
recall and solve problems using V
= IR.
Discussion: of resistance and Ohm’s law including its limitations. Formal
definitions.
Experiment: I-V characteristic of a wire (Note that the experiment is not
intended to be rigorous. Rather, it provides practice at circuit building
and meter reading).
11(f)
recall and solve problems using
P = VI,
P = I2R.
Revision of term power from Unit 2
Derivation of power = VI = I2R using V = W/Q,
P = W/t, Q = It and V = IR
Learning resources
variable d.c. supply or battery and
variable resistance, switch, length of
resistance wire, croc clips, leads,
ammeter, voltmeter (digital or
analogue).
Examples sheet including
May/June 2010 9702 paper 22
question 6(a)
May/June 2010 9702 paper 23
question 6
Oct/Nov 9702 paper 21
question 6
Examples sheet including
May/June 2010, 9702 Paper 22,
question 6(a)
Oct/Nov 2009, 9702 Paper 12,
question 30
May/June 2008, 9702 paper 2,
question 6
Oct/Nov 2007, 9702 Paper 1,
question 29
11(i)
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Sketch and explain the I-V
characteristics of: (i) a metallic
Experiment: I-V characteristic of a wire.
Plot graph for forward and reverse voltage.
Cambridge AS Level Physical Science (8780)
Variable d.c. supply or battery and
variable resistance, switch, length of
4
Syllabus ref
Learning objectives
Suggested teaching activities
Learning resources
conductor at constant
temperature,
Discussion: idea of ‘resistance’ to current flow
Resistance and ohm defined - ratio V/I, not the gradient of a graph. R
= V/I.
Note: forward and reverse voltages should be plotted for all devices.
Explanation in terms of constant resistance
enamelled constantan wire on a former,
croc clips, leads, ammeter, voltmeter,
(digital or analogue), means of
temperature control e.g. water bath and
thermometer.
Data logger etc (if available)
(ii) a semiconductor diode
Experiment: I-V characteristics of a semiconductor diode.
Note: forward and reverse voltages.
Explanation in terms of different resistance values
The ideal diode and its I-V characteristic.
Variable d.c. supply or battery and
variable resistance, switch,
semiconductor diode with protective
resistor, croc clips, leads, ammeter,
voltmeter, (digital or analogue)
Data logger etc (if available)
(iii) a filament lamp.
Experiment: I-V characteristics of a filament lamp
Note: forward and reverse voltages
Explanation in terms of increase of resistance of a metal with
temperature.
Variable d.c. supply or battery and
variable resistance, switch, filament
lamp (e.g. 12 V, 36 W), croc clips,
leads, ammeter, voltmeter, (digital or
analogue)
Data logger etc (if available)
(iv) a thermistor (thermistors will
assumed to be of the negative
coefficient type)
Experiment: temperature characteristic of a thermistor
Explanation of graph in terms of large decrease of resistance (c.f. metal)
with temperature rise
variable d.c. supply or battery and
variable resistance, switch, bead
thermistor on insulated leads, croc
clips, leads, milliammeter, voltmeter,
(digital or analogue), means of
temperature control e.g. water bath and
thermometer, warm water
Examples including:
May/June 2011 9702 paper 23
question 5
May/June 2010, 9702 Paper 23,
question 6
Oct/Nov 2009, 9702 Paper 22,
question 6
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Cambridge AS Level Physical Science (8780)
5
Syllabus ref
Learning objectives
Suggested teaching activities
Learning resources
12(c)
recall Kirchhoff’s first law and
appreciate the link to
conservation of charge.
Discussion: charge conservation leading to statement of Kirchhoff’s first
law
12(d)
recall Kirchhoff’s second law and
appreciate the link to
conservation of energy.
Discussion: energy conservation leading to statement of Kirchhoff’s
second law
12(e)
derive, using Kirchhoff’s laws, a
formula for the combined
resistance of two or more
resistors in series.
Derivation of R = R1 + R2 + ……
Expt: resistors in series
12(f)
derive, using Kirchhoff’s laws, a
formula for the combined
resistance of two or more
resistors in parallel.
Derivation of 1/R = 1/R1 + 1/R2 + ……
Expt: resistors in parallel
12(g)
solve problems using the formula
for the combined resistance of
two or more resistors in series.
Worked examples
12(h)
solve problems using the formula
for the combined resistance of
two or more resistors in parallel.
Worked examples
12(i)
apply Kirchhoff’s laws to solve
simple circuit problems.
Worked examples
Examples
May/June 2011 9702 paper 22
question 5(b)*(c)
Oct/Nov 2011 9702 paper 22
question 5**
Oct/Nov 2011 9702 paper 23
question 5***
May/June 2011, 9702 Paper 21,
question 5
May/June 2011, 9702 Paper 23,
question 5
*Redraw circuit with dotted boxes
around batteries removed, relabel
resistors R1, R2 and R3. Reword the
stem to read ’3 resistors, R1, R2 and R3.’
** Redraw circuit with dotted boxes
around batteries removed. Reword
stem (first 3½ lines) to read
‘A cell of e.m.f. E1 is connected in
series with two resistors of resistance r1
and R1 and a uniform metal wire of total
resistanceR2.
A second cell of e.m.f. E2 is connected
in series with a resistor of resistance r2
and a sensitive ammeter and is then
connected across the wire at BJ.’
*** Redraw circuit with dotted boxes
around batteries removed. Reword the
stem to read ’3 resistors, of resistance
2.3 Ω, 5.5 Ω and 1.8 Ω ’
12(j)
show an understanding of the use
of a potential divider as a source
of variable p.d.
Discussion: ‘sharing’ p.d. between two resistors in series.
Experiment: showing the use of a long wire as a potential divider
dissection of a small potentiometer with circular carbon track.
Power supply, 1 metre resistance wire
taped to a metre ruler, voltmeter,
jockey, leads
Discussion: p.d. along a current-carrying
uniform wire, V ∝ l, with conditions
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Cambridge AS Level Physical Science (8780)
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