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Electrical Energy

Based on the book "Physics & Chemistry Now!"
by

Lisa Bunda

on 5 April 2014

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Transcript of Electrical Energy

electrical
energy
ENERGY AND POWER
ENERGY
JOULES (J)
1 Ws = 1 J/s
3600 kWs = 3600 kJ
1 Kwh = 3600 kJ
[E]
_
P
E
T
X
POWER
WATT (W)
Electrical power = UxI
[P]
Joule [J]
Time [T]
Watt [W]
_
U
P
I
X
Watt [W]
Ampère [A]
Volts [V]
(Potential Difference)
(Current)
(Electrical Power)
EFFICIENCY
100 %
(Electrical Energy)
90 %
10 %
(for example)
lightbulb
Light
Heat
an efficient
efficient
wasted
EFFICIENCY
=
USEFUL ENERGY CONVERTED
ENERGY CONVERTED
X
100%
Ordinary light bulbs
Low-energy light bulbs
low efficiency
high efficiency
over long term cheaper
SHORT CIRCUIT
AND
CIRCUIT OVERLOAD
(
)
SHORT CIRCUIT
The connecting wires make contact with each other

Current does not flow through appliance

These wires have a very low resistance
[High current + Fire risk]
_
I
U
R
X
Volts [V]
Ampère [A]
Ohm [ ]
(Resistance)
(Current)
(Potential difference)
CIRCUIT OVERLOAD
Too many appliances are connected to a single group

Total power greater than maximum power allowed

You need to calculate the total power of a group to predict a circuit overload
[High current + Fire risk]
A group is protected against circuit overload by a
fuse
230 V
always
x I = max P
ELECTRICAL ENERGY AND
THE ENVIRONMENT
Fossil Fuels
gas, oil or coal
burning fossil fuels causes:
Large quantity of Carbon dioxide to be formed
Acid rain
fossil fuels
can
run out
contributes to the greenhouse effect
[
a cause of global warming
]
not always
Depends on quality fuel and
technical circumstances
Nuclear Power Plants
no air pollution
but
radioactive waste
an accident can have
huge
consequences for environment
Renewable types of energy
sustainable
WIND
WATER
SOLAR
ELECTRICAL ENERGY
Consumer associations
do not use electrical energy when not necessary
DISPOSAL PROBLEMS
batteries
chemical waste;
->heavy metal compounds

requires 50x more energy than providing

rechargeable cheaper over long term than disposable

recyclable/non-recyclable
zinc-carbon penlite

(mini) penlite battery

button cells

rechargeable battery

accumulator

small accumulator
Battery Types
cheap and relatively harmless, short life-time
more harmful, gives constant power, long life-time
harmful, but useful because of their small size
can be used in all sorts of appliances, usually recyclable
harmful, supplies high power
harmful, should not be discharged into environment
torch battery/flat battery
alkaline battery (AA/AAA size)
It is the weakest link in the chain and it will sacrifice itself in order to protect the more valuable parts in the circuit
Full transcript