AC vs. DC CurrentElectromagnetic Fields

DC Direct Current

Current that is produced in a circuit by a steady voltage source. Direct current is when electrons flow in one direction in a circuit only.

2

In direct current the voltage will go to maximum or PEAK (almost) instantly so on a graph it looks like this.

Vol

ts

Time0

Electrons flow from – to +

1 sec

AC Alternating Current• Current that is produced by a voltage source

that changes polarity, or alternates, with time.

3

In alternating current the voltage goes to PEAK positively then reverses to zero, the current then goes to PEAK in the negative.

Vol

ts

Time

0

When the electrons have gone once in each direction makes cycle and is represented with a sine wave as seen in the graph.

When armature cuts magnet field at peakWhen armature runs parallel to field at zero

http://www.walter-fendt.de/ph14e/generator_e.htmLink needs Java to run

Draw this graph on your paperDraw this graph on your paper

Electromagnetic Fields• When current flows through a

conductor a magnetic field is produced about the conductor.

• The magnetic field does not have a north or south pole but it does have direction which is determined by the direction of the current.

• A compass will deflect when in the area of these electrically induced magnetic field

Wire in a coil• Take the same wire as in the

previous slide and put the wire into a coil and now the magnetic field will have a north and south pole.

• Add an iron core and this increases the magnetic field, also called a solenoid

Solenoid Applications

• Door Bell-

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• Relay Switch-

• Speaker-

http://youtu.be/KqcT-oYImFQ

Motor Action

• When a current is applied to wire that is in a magnet field the field created by the electron flow causes a force that will repel the wire causing it to move. This is called motor action.

Electric Motors

• An electric motor uses the principle of the repelling force to turn electrical energy into mechanical energy.

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