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Applications of Electromagnetism. Electromagnetic Waves.

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Presentation on theme: "Applications of Electromagnetism. Electromagnetic Waves."— Presentation transcript:

1 Applications of Electromagnetism

2 Electromagnetic Waves

3 A changing magnetic field generates an electric field. B E A changing electric field generates a magnetic field. E B

4 changing E ELECTROMAGNETIC WAVE speed = c (speed of light; 3.00 x 10 8 m/s) changing B changing E changing B

5 EM Wave

6 E B v v

7 EM waves produced by accelerated electric charges. To produce an EM wave:

8 Electromagnetic Spectrum v = λ f

9 Transformers

10 A changing magnetic field in the primary coil induces a current in the secondary coil.

11 Use an alternating current to produce a constantly changing magnetic field.


13 EMF in a coil depends on the number of turns of wire in that coil. Step-up Transformer EMF α N

14 Step-Down Transformer Secondary coil has fewer turns (N) than the primary. EMF s N s = EMF p N p

15 Power in a Transformer If there are no losses (ideal transformer), Power primary = Power secondary Power = voltage x current EMF p x I p = EMF s x I s since voltage = EMF

16 Step-up transformer: increases EMF, decreases current Step-down transformer: decreases EMF, increases current EMF α 1/I

17 Electric Power Transmission Power loss in wires occurs when current is high. Use step-up transformer to transmit power at high emf and low current (minimize power loss).

18 Electric Motor

19 Motor: Converts electrical energy into mechanical energy.


21 Commutators – switch the current direction in the armature coil every half turn wire wrappings which turn field poles

22 In an A.C. motor, input electricity continually switches direction; commutators not needed.





27 Maximum induced current when cutting through lines of magnetism

28 With each ½ turn, wire in the armature changes its direction of motion in magnetic field. Induced Alternating Current

29 A.C. Generator

30 D.C. Generator To produce an output of D.C., use commutators to switch current direction.

31 Motor vs. Generator Motor: converts electrical energy to mechanical energy Generator: converts mechanical energy to electrical energy

32 When a motor is spinning, it also acts as a generator and generates an EMF opposite the supplied EMF. This is called the back EMF.

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