Slide 1
Basic
Electrical
Principles
Slide 2
Basic Electrical Principles
There are THREE basic
components to an
electrical circuit
Slide 3
Basic Electrical Principles
1.Voltage (V)
2. Current (A)
3. Resistance (R)
Slide 4
Basic Electrical Principles
1.Voltage (V)
Explain difference between mains
and direct voltage.
(Measured in Volts)
Force used to push current around
a circuit
This can be A.C.
(Alternating Voltage [Mains])
Or D.C.
(Direct Voltage [Battery])
Slide 5
Basic Electrical Principles
2. Current (A)
(Measured in Amps)
The flow of electrons around a
Circuit.
This can be A.C.
(Alternating Current [Mains])
Or D.C.
(Direct Current [Battery])
Slide 6
Basic Electrical Principles
3. Resistance (R)
(Measured in Ohms [Ω])
This is the resistance to current
flow that all things have.
Some are very low – Copper Wire
(Conductors)
Give example of Conductors, ask
for suggestions of other possible
conductors. Most metals, silicon
(transistors), water.
Slide 7
Basic Electrical Principles
3. Resistance (R)
(Measured in Ohms[Ω])
This is the resistance to current
flow that all things have.
Some are very low – Copper Wire
(Conductors)
Some are very high – Plastic
(Insulators)
Give examples of Inulators, plastic
sleeving, rubber, ask for
suggestions of other possible
insulators. Glass, wood, textiles,
paper/cardboard.
Slide 8
Basic Electrical Principles
Ohms Law
Ohms law states that the current through a
conductor between two points is directly
proportional to the potential difference
across the two points.
Slide 9
Basic Electrical Principles
Power (W)
(Measured in Watts)
Power is the rate at which
electrical energy is transferred
by an electrical circuit
i.e. how quickly it uses power
Or ‘how long the battery lasts’
Bi-product of an electrical circuit
Can be ‘felt’ as heat and is how
devices are described, 60W bulb,
2.5KW fire etc.
Slide
10
Basic Electrical Principles
Power Calculation
(Measured in Watts)
Power (W) = Voltage (V) x Current (A)
or
Slide
11
Basic Electrical Principles
Fuses
Fuses are used to protect the circuit.
They protect the cable from too much
current being allowed to flow
& protect the device from damage
if it goes into fault.
Slide
12
Basic Electrical Principles
Fuse Calculation
To calculate the correct fuse we use
Ohms Law but because often we do
not know the resistance then we
can use the power formula:
Show different types of fuse we
normally use, Blade, Maxi and
Mega.
Slide
13
Basic Electrical Principles
Fuse Calculation
To calculate the correct fuse
we use Ohms Law but
because often we do not know
the resistance then we can
substitute power
so
becomes
Slide
14
Basic Electrical Principles
Fuse Calculation
Therefore if we have
a 48W worklight and it is
Fitted on a 12v vehicle:
Slide
15
Basic Electrical Principles
Cable Types
There are two types of cable:
Stranded core – Vehicles & flexible
cables (toaster, irons, tv etc)
Show samples of cables used.
Slide
16
Basic Electrical Principles
Show sample of solid core cable.
Cable Types
There are two types of cable:
Stranded core – Vehicles & flexible
cables (toaster, irons, tv etc)
Solid core – Mains installations
Slide
17
Basic Electrical Principles
Cable Colours
Cable colours are mostly optional
except for regulated installations.
Solid & Striped
for example:
IEE 17th Edition Wiring Regulations
Earth Cable MUST BE Green/
Green/Yellow
Show samples of cables with
different colours and stripes.