Ch. 3 Ch. 3 Sec. 2 Electricity, Sec. 2 Electricity,

Magnetism & MotionMagnetism & Motion

Electrical & Mechanical Electrical & Mechanical EnergyEnergy

= ability to move an object = ability to move an object some distancesome distance

=assoc. w/ =assoc. w/ electric currentselectric currents

= due to an = due to an object’s movement or positionobject’s movement or position

Energy

Mechanical energy

Electrical energy

When current-carrying wire is placed in magnetic field,When current-carrying wire is placed in magnetic field,

electrical energy electrical energy mechanical energy mechanical energy

GalvanometerGalvanometer Device that measures small currentsDevice that measures small currents Converts electrical energy Converts electrical energy

mechanical energymechanical energy HOW IT WORKS:HOW IT WORKS:

Current passes thru loops of wire in Current passes thru loops of wire in magnetic fieldmagnetic field

Magnetic field from wire interacts Magnetic field from wire interacts with magnet’s fieldwith magnet’s field

Causes loops of wire & pointer Causes loops of wire & pointer attached to loops to rotate ½ turnattached to loops to rotate ½ turn

Current does not reverseCurrent does not reverse

GalvanometerGalvanometer

Electric MotorElectric Motor Device that uses electric current to Device that uses electric current to

turn axleturn axle Converts electrical energy Converts electrical energy

mechanical energymechanical energy Loop of current-carrying wire spins Loop of current-carrying wire spins

continuouslycontinuously

Parts of a MotorParts of a Motor

device that device that reverses flow reverses flow of current of current

Brushes and commutator

CommutatoCommutatorr==

Parts of a MotorParts of a Motor

contact points contact points that connect that connect commutator to commutator to current sourcecurrent source

Brushes and commutator

BrushesBrushes==

Parts of a MotorParts of a Motor

wires wrapped wires wrapped around iron around iron corecore

Armature

ArmatureArmature==

armaturearmature

Armature

In this figure, the armature winding has been left out so that it is easier to see the commutator in action. The key thing to notice is that as the armature passes through the horizontal position, the polesof the electromagnet flip. Because of the flip, the north pole of theelectromagnet is always above the axle so it can repel the field magnet's north pole and attract the field magnet's south pole.

MOTORS EVERYWHERE !

Look around your house and you will find that it is filled with electric motors.

The fan over the stove and in the microwave oven

The blender The can opener

The refrigerator – Two or three in fact: one for the

compressor, one for the fan inside the

refrigerator, as well as one in the icemaker The mixer

Probably even the clock on the oven.

Starting in the kitchen, there are motors in:

In the garage, there is an In the garage, there is an electric motor inelectric motor in

The The washerwasher The The dryerdryer The The electric screwdriverelectric screwdriver The vacuum cleanerThe vacuum cleaner The electric saw The electric saw The electric drill The electric drill

The fan The fan The electric The electric

toothbrush toothbrush The hair dryer The hair dryer The electric razor The electric razor

Even in the bathroom, there’s a motor in: