Topic 3: Electric Circuits
0.3 Specification notice:
In order to develop their practical skills, students should be encouraged
to carry out a range of practical experiments related to this topic. Possible
experiments include estimating power output of an electric motor, using a
digital voltmeter to investigate the output of a potential divider and
investigating current/voltage graphs for a filament bulb, thermistor and
diode.
Mathematical skills that could be developed in this topic include
substituting numerical values into algebraic equations using appropriate
units for physical quantities and applying the equation y = mx + c to
experimental data.
This topic may be studied using applications that relate to electricity, for
example, space technology.
3.Q Exam questions
Why does an increase in temperature Particles vibrate more frequently (1)
increase resistance? therefore collide more frequently
with charge carriers (1) preventing
them from flowing through so easily
Describe the 6 steps in which filament bulbs ● As PD increases current increases
have their resistance affected? (Miss Hartley and electrons begin to move faster
with more KE (1)
● Electrons collide with the lattice of
positive ions and transfer KE to the
lattice of positive ions (LOPI) (1)
● Increases the amplitude of vibrations
of LOPI (1)
● Increases the temperature (of the
filament) (1)
Script)
● Increases the rate of collisions
between e and LOPI which increases
the resistance (1)
● Less increase for I for the same
increase in PD (1)
Explain the shape of the IV graph for the ● As PD increases current increases
thermistor? (6) (Miss Hartley Script) ● As the current increases the
, temperature increases (1)
● As the temperature increases more
electrons are promoted from the
valence band to the conduction band
and become free to move (1)
● This increases the charge carrier
density (1)
● This causes the current to increase
according to I=nAve where A,v and e
are constant (1)
● Therefore the resistance must have
decreased (1)
● Less increase for I for the same
increase in PD (1)
3.31 Understand that electric current is the rate
of flow of charged particles and be able to use
the equation I=∆Q/∆T
What is electric charge? The physical property of matter that causes it to experience a
force when placed in an electromagnetic field
What is current? ● The rate of flow of charge
● 1A is 1C flowing via a point every second
What is 1 Coulomb? The charge that flows past a point in one second when there
is a current of 1 amp
What is the circuit symbol
of a switch?
What is the circuit symbol
of a cell/battery?
What is the circuit symbol
for a diode?
, What is the circuit symbol
of both a resistor and a
variable resistor?
Variable resistor or potentiometer
What is the circuit symbol
of Light Emitting Diode
(LED) ?
What is the circuit symbol
of a lamp?
What is the circuit symbol
of a fuse?
What is the circuit symbol
of a voltmeter?
What is the circuit symbol
of an ammeter?
This ideally should have zero resistance
What is the circuit symbol
of a thermistor?
What is the circuit symbol
of an Light Dependent
resistor (L.D.R)
What is conventional The flow of positive charge from the positive terminal of a cell
current? to the negative terminal
What happens to the ● The current is the same at all points
current, total potential ● The total potential difference of the power supply is
difference and total shared between components
resistance in a series ● The total resistance of two components is the sum of
circuit? the resistance of each component
0.3 Specification notice:
In order to develop their practical skills, students should be encouraged
to carry out a range of practical experiments related to this topic. Possible
experiments include estimating power output of an electric motor, using a
digital voltmeter to investigate the output of a potential divider and
investigating current/voltage graphs for a filament bulb, thermistor and
diode.
Mathematical skills that could be developed in this topic include
substituting numerical values into algebraic equations using appropriate
units for physical quantities and applying the equation y = mx + c to
experimental data.
This topic may be studied using applications that relate to electricity, for
example, space technology.
3.Q Exam questions
Why does an increase in temperature Particles vibrate more frequently (1)
increase resistance? therefore collide more frequently
with charge carriers (1) preventing
them from flowing through so easily
Describe the 6 steps in which filament bulbs ● As PD increases current increases
have their resistance affected? (Miss Hartley and electrons begin to move faster
with more KE (1)
● Electrons collide with the lattice of
positive ions and transfer KE to the
lattice of positive ions (LOPI) (1)
● Increases the amplitude of vibrations
of LOPI (1)
● Increases the temperature (of the
filament) (1)
Script)
● Increases the rate of collisions
between e and LOPI which increases
the resistance (1)
● Less increase for I for the same
increase in PD (1)
Explain the shape of the IV graph for the ● As PD increases current increases
thermistor? (6) (Miss Hartley Script) ● As the current increases the
, temperature increases (1)
● As the temperature increases more
electrons are promoted from the
valence band to the conduction band
and become free to move (1)
● This increases the charge carrier
density (1)
● This causes the current to increase
according to I=nAve where A,v and e
are constant (1)
● Therefore the resistance must have
decreased (1)
● Less increase for I for the same
increase in PD (1)
3.31 Understand that electric current is the rate
of flow of charged particles and be able to use
the equation I=∆Q/∆T
What is electric charge? The physical property of matter that causes it to experience a
force when placed in an electromagnetic field
What is current? ● The rate of flow of charge
● 1A is 1C flowing via a point every second
What is 1 Coulomb? The charge that flows past a point in one second when there
is a current of 1 amp
What is the circuit symbol
of a switch?
What is the circuit symbol
of a cell/battery?
What is the circuit symbol
for a diode?
, What is the circuit symbol
of both a resistor and a
variable resistor?
Variable resistor or potentiometer
What is the circuit symbol
of Light Emitting Diode
(LED) ?
What is the circuit symbol
of a lamp?
What is the circuit symbol
of a fuse?
What is the circuit symbol
of a voltmeter?
What is the circuit symbol
of an ammeter?
This ideally should have zero resistance
What is the circuit symbol
of a thermistor?
What is the circuit symbol
of an Light Dependent
resistor (L.D.R)
What is conventional The flow of positive charge from the positive terminal of a cell
current? to the negative terminal
What happens to the ● The current is the same at all points
current, total potential ● The total potential difference of the power supply is
difference and total shared between components
resistance in a series ● The total resistance of two components is the sum of
circuit? the resistance of each component
