1. Electromagnetic induction When magnet field lines are broken, current flows in the conductor. (2 ways to cut) (Magnet with a coil breaking the fields induces current.)

2. Electromagnetic induction Current must flow so as to make the near end of coil same as pole of magnet. Use right hand grip rule with thumb pointing to the north, then fingers show direction of current.

3. Lenz’s Law The direction of the induced current is always such as to oppose the change producing it.

4. Electromagnetic induction Which direction must the current flow in to make the near end south?

5. Electromagnetic induction Which direction must the current flow in to make the near end north?

6. Direction of induced current Fleming’s right hand rule

7. Used to determine direction of current flow in the conductor

8. a.c. generator

10. End of generators for now……

11. Starting the transformer principle

12. Mutual induction

13. transformer If an alternating current is on the primary coil, this sets up an alternating magnetic flux in the coil and this induces an alternating e.m.f. in the secondary coil. Mutual inductance used in this way is called a transformer.

14. Step up, step down Step up Larger Output e.m.f. Step down Smaller Output e.m.f.

15. Turns ratio Secondary e.m.f = no. of turns in secondary Primary e.m.f. no. of turns in primary P = VIP = I 2 R Power equations

16. Practical transformers…reducing energy losses Low resistance copper coils reduces internal energy losses Laminated core to reduce Eddy’s current. Soft iron core reduce energy required to bring about magnetic reversals. Efficient core design the link all the primary flux with the secondary coil.