1. Combined Science (1-9): Electromagnetism The Motor Effect

2. Objectives:

3. Transformers and the National Grid
Draw a line under last lesson’s work and write today’s title in your book...
Transformers and the National Grid
21/11/2018
c/w

4. FLASHBACK
FLASHBACK: Explain how an alternating current can be induced by a magnet bouncing in a coil of wire

5. What is meant by the ‘national grid’?
Starter Activity
What is meant by the ‘national grid’?

6. Explore: National Grid
Once a power station has generated energy to make a turbine spin, this will spin a generator.
The current that is then induced must pass through to our homes, which can be a substantial distance. This is why we must use TRANSFORMERS

7. Task: Suggest how we could INCREASE the amount of induced current?
Explore:
Transformers
Transformers are essentially blocks of iron with different numbers of coils wrapped around each side. They are able to alter the voltage in order to change the current
STEP UP transformers will increase the voltage to decrease current
STEP DOWN transformers will decrease the voltage to increase current
Task: Suggest how we could INCREASE the amount of induced current?

8. UP VOLTAGE DOWN CURRENT DOWN VOLTAGE UP CURRENT
STEP UP transformers will increase the voltage to decrease current
STEP DOWN transformers will decrease the voltage to increase current
UP VOLTAGE
DOWN CURRENT
DOWN VOLTAGE
UP CURRENT
Task: In pairs, discuss why we have to decrease the current before it travels over the lines toward our homes

9. Explore: Transformers
In order to get the power to travel through the significant distance of wires, we need to use a step UP transformer to increase the voltage to reduce the current.
We do this as large currents cause a lot of heat energy to be dissipated into surroundings. This is how we manage to increase efficiency (reducing loss).
Task: Suggest then what STEP DOWN transformers do and why they need to do it!

10. Explore: Transformer Structure Np= Ns= Vp= Vs=
As discussed, a transformer is an iron core with wires wound around each side. The input is known as the primary coil and the output is known as the secondary coil. More coils on the secondary? Then you have a STEP UP!
Np=
Ns=
Vp=
Vs=
Copy this diagram down and then fill in the box on the left with the data given

11. Explore: Transformer Structure Np= 100 Ns= 250 Vp= 120 Vs= ?
There is a very simple ratio equation that links the number of coils to the voltage. For example, if there are double the amount of coils on the secondary than on the primary, then the voltage also doubles!
Np= 100
Ns= 250
Vp= 120
Vs= ?
Task: try this equation to calculate the voltage coming out of the secondary part of the transformer. Hint: put values in and then calculate one side of the equation first.

12. Explore: Transformer Structure Np= Ns= Vp= Vs=
As discussed, a transformer is an iron core with wires wound around each side. The input is known as the primary coil and the output is known as the secondary coil. More coils on the secondary? Then you have a STEP UP!
Np=
Ns=
Vp=
Vs=
Copy this diagram down and then fill in the box on the left with the data given