Electricity
Dec 31, 2015
Electricity
•Static• Is stationaryE.g. Brush your hair
Wool socks in tumble drier
•Current• Flows around
circuitE.g. turn on light
Computer
Electricity occurs in 2 different forms
Static Electricity
• Occurs with materials which are insulators
• Rubbing adds or removes electrons
• Object becomes charged• Like objects repel, unlike attract
Current Electricity
• Electrons flow through a conductor• Negative to positive• Circuit = continuous loop for
electrons to flow• Needs energy supply• Energy user
Electrical components
• Wire• Ammeter• Battery• Fuse• Connected
wires
• Bulb• Switch• Voltmeter• diode• Resistor• Rheostat
CIRCUIT TYPESThe simplest type of circuit involves electricity going around with no “choices” (electrons don’t really choose).
This is called a Series circuit.
Draw the path the electrons travel.
The other main type of circuit has two or more branches.
This is called a Parallel circuit.
Draw on the electron flow.
What sort of circuit is this?
A parallel… but, more importantly…
A short circuit.
Series circuit
• Has a single loop for electrons to travel round
• Components are connected one after another
• Current has to travel through all components
• Current is the same at all points• Voltage is shared between
components
Parallel circuit
• Has two or more paths for electrons to flow down
• Current is shared between the branches
• Sum of the current in each branch = total current
• Voltage loss is the same across all components
Current (I)
Current is the flow of electronsaround a circuit• DC = direct current like battery• Electrons flow in one direction• AC = Alternating current like mains• Electron flow changes direction
60x per second
Ammeter
• Measures CURRENT(I)• Unit = Amp (A)• Current is flow of electrons• Connect in series at the point you
wish to measure• RED to RED and BLACK to BLACK
3 pin plug
• 3 wires• P = phase (brown or red)• N = neutral (blue or black)• E = earth (yellow/green or green)
Voltage (V)
Gain or loss of energy as itpasses through a component• Voltage lost = voltage gained• In series voltage loss is shared
between components• In parallel voltage loss is the same
across all components
Voltmeter
• Measures voltage• Unit = Volt (V)• Voltage increases as it passes
through energy suppliers• Voltage is decreased as it passes
through users• Connect in parallel around a
component
SUMMARY
In Series In Parallel
Current
Voltage
Always the same The branches share electrons and add to the total
Voltage from source = voltage used
Voltage is shared between power users
Voltage is the same in all branches
Resistance (R)
The amount that a component slows the current
•As the electrons are slowed by a resistor, energy is lost in the form of heat.
•This means that current, resistance and voltage must be linked.
•This is Ohms law
•The unit of resistance is the ohm, symbol V
I R×
Power
Energy used by component per second
• Unit of power is the Watt, symbol is W• One watt means that 1 joule of electrical
energy is being used up per second.• Current, voltage and power
are linked P
I V×