Producing & transporting electrical energy

Producing & transporting electric energy
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NatuurkundeMiddelbare schoolhavo, vwoLeerjaar 2,3

This lesson contains 51 slides, with interactive quizzes, text slides and 19 videos.

time-iconLesson duration is: 30 min

Items in this lesson

Producing & transporting electric energy

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Slide 2 - Video

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s

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Slide 5 - Video

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You can explain how electric energy is produced

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Dynamo/ generator
Try this 
You can produce your own electricity just by changing the magnetic field near a copper coil.

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1

Slide 20 - Video

02:17
Wat does a generator do and what do you need to build one?

Slide 21 - Open question

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380 kV
10 kV
230 V
supplied energy
consumed energy
Energy loss 
E = P.t
P=UI=I2R

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Slide 26 - Video

When current flows through a wire, the wire can become hot.

Think back to Ohm's law: 
The current will then be:

Increasing the Voltage (U) will result in an equal increase in current (I) under the condition that the resistance (R) of the wire stays constant. Increasing the current, however will also increase the risk of electron particles colliding with each other. These collisions result in friction (increasing R of the wire) which causes heat, a form of energy loss.

The powerplant only produces a certain amount of energy (E) during the day (t). Preferably all of the produced energy is delivered to the factories and households without any losses occuring during transport.

You can calculate the supplied power using: 

To calculate the consumed power at home: 

Without any energy loss (efficiency = 100%), the consumed power will be the same as the supplied power. But normally the efficiency is not a 100% because of heat loss during transport. A big current will directly increase the amount of heat loss because of the friction of the electrical particles in the wire. Therefore you want to keep this current as small as possible. The way to do this is by increasing the Voltage using transformers 

Rewriting the formula                         will make it clear why it is vital to lower the current by increasing the Voltage. First thing to do is to replace U with I.R

Doing this will result in: 



As you can see the power lost is equal to the root of the current. Therefore lowering the current will have a big impact.


P=UI=IRI=I2R
U=IR
I=RU
P=tE
P=UI
P=UI

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QUANTITIES
UNITS
Voltage
Current
Resistance
Power
Energy
Time
U
I
R
P
E
t

Voltage
Ampere
Ohm
Watt (Joule/second
kiloWatthour
hour (second)
V
A
Ω
W (J/s)
kWh
h (s)
FORMULAS
U=IR
P=UI
E=Pt
1 W = 1 J/s       1 kWh = 3,6 MJ   

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Transformers
Transformator are used to increase or decrease the Voltage in a wire and thereby decreasing or increasing the  current.

The secondary coil is influenced by the magnetic field going through the transformer core. You can change this field at the primary input side. The number of turns of each coil will ultimately decide if the Voltage at the seconday coil will go up or down.


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Example
In this example the Voltage is decreased from 24 Volts to just 12 Volts. This is because the number of windings in  the secundary side are halved (from 10 to 5). 

If the secundary coil had 100 windings instead, the Voltage would have increased ten fold to 240 Volts.

The output voltage is equal to the ratio of the numer of turns on the primary & secondary coils times the input voltage.


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Slide 32 - Video

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FORMULA
UsUp=NsNp
      = Voltage at the primary coil

      =Voltage at the secondary coil

      = Number of turns primary coil

      = Number of turns secondary coil
Up
Us
Np
Ns

Slide 37 - Slide

What Voltage do we use at home?
A
20 kV
B
380 kV
C
10 kV
D
230 V

Slide 38 - Quiz

Why do we need to increase the voltage in the transmission lines?
A
Safety reasons
B
To prevent energy loss
C
For a stable frequenty of 50 Hz
D
That is what devices need

Slide 39 - Quiz

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timer
15:00

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Rendement

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Transformator

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