1.
202/1 – Know the principles of
electricity
Outcome 1.2/1.3 – Sources of
electromotive force & current
effects
Unit 202 Principles of electrical
science
2.
1.1 Describe the reaction of electrons
when charged to form an electric
current
Last session
3.
Unit 202 Principles of electrical
science
Unit 202 summative assessment
June 2015 (TBC)
4.
1.2 Identify sources of an electromotive
force
MAGNETIC
CHEMICAL
THERMAL
1.3 Describe the effects of an electric
current
This session
26.
Build a potato cell
Measure output voltage
Connect all ‘potateries’
in series(anode to cathode)
Calculate the output voltage
Measure the output voltage
Potato battery
27.
A D.C. generator does not have slip
rings, instead it has a commutator.
A commutator keeps the positive end
of the loop connected to one of the
output cables.
d.c. generator or dynamo
30.
Heating - The heating effect of electric current is used in many everyday devices.
Electric cookers, kettles and toasters are among the household appliances that rely on it.
Joule’s Law states that the rate at which heat is produced in a resistor is proportional to
the square of the current flowing through it, if the resistance is constant
Chemical - Passing an electric current through a liquid causes chemical changes in a
process called electrolysis. Electroplating uses electrolysis to put a layer of one metal on
top of another. Examples include chromium plating of bathroom and car parts, and
silver plating of cutlery and jewellery.
Magnetic - Electric current passing through a wire generates a magnetic field around
the wire. This effect is used in all sorts of ways. Examples include electric motors and
electromagnets. In a car, for example, the central locking uses electromagnets called
solenoids to operate the lock mechanism. Another widespread example is the
loudspeaker, where variations in the magnetic effect of an electric current are
translated into sound waves that we can hear.
Describe the effects of an
electric current
31.
REMEMBER - If a coil of cable is
rotated in a magnetic field
It will generate a voltage.
Magnetic effect
When an electric current passes
through a conductor a magnetic field
appears around it.
The magnetic field increases when the
wire is formed into a coil.
If the coil is wound on an iron core the
iron will become magnetised.
32.
In 1821 Thomas Seebeck discovered a thermal
effect of electrical current.
If two dissimilar metals were connected together
at one end and heat was applied, a voltage
appeared at the cooler open end.
Thermal effect
33.
As the difference in temperatures T1 and T2
increases, so does the voltage.
Through tests, a specific voltage will indicate a
specific temperature. This is called a?
The Seebeck effect
34.
As the difference in temperatures T1 and T2
increases, so does the voltage.
Through tests, a specific voltage will indicate a
specific temperature. This is called a?
thermocouple
The Seebeck effect
36.
Where could a thermocouple be used?
Ovens
Water heaters
Furnaces
hair straighteners
Thermocouple
37.
Describe the chemical and thermal effects of electrical
currents.
Two DISIMILAR metals and an electrolyte make a _______
This is a _________ effect of electrical current.
A secondary cell can be?
Magnetic effect?
Seebeck discovered a ____________ effect of electrical current.
This device is called a ________________.
A difference in _____________ will create a voltage at the open end.
consolidation
38.
1.2 Identify sources of an electromotive
force
MAGNETIC
CHEMICAL
THERMAL
1.3 Describe the effects of an electric
current
Consolidation
39.
1.4 Identify SI Units for various
electrical quantities
Current, potential, resistance, resistivity,
temperature, mass, force, magnetic flux,
magnetic flux density, period, frequency,
power, energy, time, length, area, mass,
weight.
1.5 Transpose basic formulae.
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