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Electricity

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Electricity
Electricity
Electrons
• Electrons are tiny charges
found inside atoms
• They have a negative
charge
• Protons have a positive
charge
• Electrons fly around the
outside of an atom, they
can be rubbed off
Charges
• No charge- Equal numbers of electrons and
protons
• Positive charge- Less electrons
• Negative Charge- More electrons
Static Electricity
• This is when electrons build up on
certain materials
• If you wear tracksuits you might find that
you get electric shocks
• The nylon rubs electrons on to you as
you walk
• Your body builds up electrons and these
jump as a shock when you touch metal
Static Electricity
• This is why you can stick balloons to the
wall
• This is how the Van de Graaf works
• Like charges repel
• Opposite charges attract
The Dangers
• AC electricity in the house is 240 Volts, but
it is 100- 400kV at pylons
• Lightning carries 100, 000, 000 Volts of
electricity (heating the air to 28,000oC)
• Lightning is an example of static electricity
• Ice particles in a cloud get charged and
the electricity takes the path of least
resistance during a thunder storm
Current Electricity
• Electrons can flow through conductors
like metals
• A circuit needs a battery to send out
electric current
• It also needs to be a complete circuit,
with no gaps
• It does not travel through insulators
Electric Symbols
Drawing Circuit Diagrams
•
•
•
•
We use symbols to draw circuits
Circuits are square or rectangular
All circuits need a battery
If you can move your finger from one end of the
battery right around the circuit to the other end it will
work
Fuses
• Fuses
• 3A Lamp
• 5A TV, Hairdryer,
Fridge
• 13A Electric fires,
washing machines
• 30A Cookers
Current
• Current is the amount of electrons flowing
through a circuit
• It is measured in Amps (A)
• Current is measured by an Ammeter
• In a series circuit the current is always
the same
• In a parallel circuit the current changes
Current in a series circuit
• The current is the same everywhere in the
circuit
• The current is 0.5A
Adding more batteries
• With one
battery the
current is 0.5A
• With two
batteries the
current is
doubled
• With three it is
tripled
Adding more components
1.0 A
divided by
three
1.0 A
divided
by two
• Each light bulb has resistance which slows down
the current
Current in a series circuit
• Current is the same everywhere in the
circuit
Current in parallel circuits
• Current is shared between the branches of
a parallel circuit
0.2A
0.1A
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