1. AC & DC Generators LEARNING OUTCOMES: Recognise the differences between DC and AC and illustrate them diagrammatically Describe how simple generators work using the dynamo effect.

2. DC= DIRECT CURRENT The current flows in one direction, from + to -. Eg, a battery AC = ALTERNATING CURRENT The current keeps reversing direction, since the 2 terminals alternately become + and – Eg, mains electricity (in the UK it alternates 50 times per second, so frequency = 50Hz). If we know how long 1 wave lasts for (the period) then the inverse is the frequency. Eg, waves lasts for 0.1s, so the frequency is 1 / 0.1 = 10Hz.

3. Electromagnetic Induction If You push a magnet into a coil the electrons in the coil are also given a push. This makes an ‘induced voltage’ N The ‘field lines’ have to be cut. No current is produced if the magnet is not moving!

4. Electromagnetic Induction If You pull a magnet out of the coil the electrons in the coil are once again given a push. This makes an ‘induced voltage’ in the opposite direction N Notice the needle moves in the opposite direction

5. How Can You Increase the Size of the Induced Current? 1.Move the Magnet Faster 2. Use a Stronger (not bigger!) Magnet 3. Put more Turns on the Coil

6. We can use a magnet, coil and movement to generate electricity with this device Will it make AC or DC Current?

7. This is a Generator You will have heard them near road works generating the electricity to make the traffic lights and machines work

8. AC Generator Induced current can be increased in 4 ways: 1)Increasing the speed of movement 2)Increasing the magnetic field strength 3)Increasing the number of turns on the coil 4)Increasing the area of the coil

9. Bikes often have Dynamos to make electricity to light a bulb Dynamos are slightly different from generators as they rotate the magnet

10. Power stations & Efficiency LEARNING OUTCOMES: Describe how the dynamo effect is used in conventional power stations to generate electricity: burning fuel producing steam spinning a turbine turbine turns generator. Be able to use equations to calculate efficiency in a variety of situations. Describe & recognise that there is significant waste of energy in a conventional power station.

13. Transformers LEARNING OUTCOMES: Explain how transformers are used on the National grid to transmit electricity at high voltage to reduce energy waste/costs. Explain how, for a given power, increased voltage reduces current. This will decrease energy waste by reducing heating of cables.