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Electrodynamics

K Warne

THE ELECTRIC MOTOR

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Magnetic EffectA magnetic field is generated around any conductor

when an electric current flows through it.

Electric current

Wire with current

coming towards

you Wire with current

going away from

you

x

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C

THE ELECTRIC MOTOR

N

current

S

Current

Magnetic

Field

Thrust

A

B

D

+ -

Rotation

Thrust

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THE ELECTRIC MOTOR

• Indicate the polarity of the battery.

• Show how the direction of rotation supports your decision.

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Electric Field Strength

N S

+ -Magnetic field Strength (B) measured

in Tesla’s (T)

Thrust

1 Tesla is the field strength when a current of 1 A flows through a

conductor and it experiences a force of 1N per meter of length.

(1A)

(1N)

(1T)

• Total number of field lines is called magnetic flux () measured in Webers (Wb)

= BA• = magnetic flux (Wb)

• B = magnetic field strength (T)

• A = area through which flux passes

= no

lines in

that

area

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Generator - dynamo

• Direct current is produced.

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Alternating and Direct Current • What would be the equivalent constant/direct current /voltage to

give the same effect as an alternating current?

??

X

~

X

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Power Transmission

Reducing the current ensures less voltage/power lost in transmission.

25 000V

0,6A

0.6 A

Cable resistance

200 km 10 Ω

Voltage drop

V = IR = (0,6)(10) = 6.0 V

Power lost = VI

= (6.0)(0.6)

= 3.6 W

250 000V

0,06A

0.06 A

Cable resistance

200 km 10 Ω

Voltage drop

V = IR = (0,06)(10) = 0.6 V

Power lost = VI

= (0.6)(0.06)

= 0.036 W

P = VI = (25000)(0.6) = 15 000 W P = VI = (250000)(0.06) = 15 000 W

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Hi…

This is a SAMPLE presentation only.

My FULL presentations, which contain a lot more slides and other resources, are freely available

on my resource sharing website:

www.warnescience.net(paste into your browser if link above does not work)

Have a look and enjoy!

Keith Warne

WarneScience