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3 Electromagnetic Induction

4 Quiz 1.Who discovered electromagnetic induction? a)Michael Faraday b)Thomas Edison c)Joseph Henry 2.A transformer is used to step-up or step-down what? 3.An electric motor is very similar to… a)a car battery b)an electric generator c)a radio receiver

5Recap ► All magnetism is caused by moving electric charge

6Recap ► A charged particle moving through a magnetic field is deflected.

7Recap ► All magnetism is caused by moving electric charge ► A charged particle moving through a magnetic field is deflected. ► Moving electric charge (like in a wire) sets up a magnetic field around it.

8 Michael Faraday and Joseph Henry discovered the principle of electromagnetic induction at almost the same time but in countries separated by an ocean!

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12 Summing Up So Far ► Moving current in a wire induces a magnetic field.  Converting electrical energy into mechanical energy, as in a motor ► Moving a magnet through coils of wire induces voltage and thus current.  More loops = more voltage = more current.  Converting mechanical energy into electrical energy, as in a generator

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14 Faraday’s Law The induced voltage in a coil is proportional to the product of its number of loops, the cross-sectional area of each loop, and the rate at which the magnetic field changes within those loops.

15 Uses For Electromagnetic Induction ► Guitar Pickups

16 Uses For Electromagnetic Induction ► Guitar Pickups ► Computer Disk Storage

17 Uses For Electromagnetic Induction ► Guitar Pickups ► Computer Disk Storage ► Smart Traffic Lights

18 Uses For Electromagnetic Induction ► Guitar Pickups ► Computer Disk Storage ► Smart Traffic Lights ► Airport Metal Detectors

19 Uses For Electromagnetic Induction ► Guitar Pickups ► Computer Disk Storage ► Smart Traffic Lights ► Airport Metal Detectors ► Earthquake Detectors

20 Uses For Electromagnetic Induction ► Guitar Pickups ► Computer Disk Storage ► Smart Traffic Lights ► Airport Metal Detectors ► Earthquake Detectors ► This list goes on and on! Electromagnetic induction led to the industrial revolution and to our current technological age.

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31 Primary Voltage Secondary Voltage Primary Voltage Secondary Voltage # of primary turns# of secondary turns =

32 Primary Voltage Secondary Voltage Primary Voltage Secondary Voltage # of primary turns# of secondary turns = Power into Primary = Power out of Secondary

33 Primary Voltage Secondary Voltage Primary Voltage Secondary Voltage # of primary turns# of secondary turns = Power into Primary = Power out of Secondary (Voltage x Current) primary = (Voltage x Current) secondary

34 1. If 100 V of ac is put across a 100-turn transformer primary, what will be the voltage output if the secondary has 200 turns? 2. The secondary is connected to a flood lamp with a resistance of 50 ohms. What will be the ac current in the secondary circuit?

35 3. What is the power in the secondary coil? 4. What is the power in the primary coil? 5. What is the ac current drawn by the primary coil?

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37 Self-Induction

38 ► Almost all transmitted by ac because it is easy to step up or down the voltage. ► With large current, you lose a lot of energy to heat, so usually transmitted at high voltage, low current. Power Transmission

39 James Clerk Maxwell

40 James Clerk Maxwell An electric field is induced in any region of space in which a magnetic field is changing with time.

41 James Clerk Maxwell An electric field is induced in any region of space in which a magnetic field is changing with time. A magnetic field is induced in any region of space in which an electric field is changing with time.