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

Magnetism & MotionMagnetism & Motion

energyenergy ability to move ability to move an object some an object some distancedistance

electrical electrical energyenergy

energy assoc. w/ energy assoc. w/ electric currentselectric currents

mechanical mechanical energyenergy

energy due to an energy due to an object’s movement object’s movement or positionor position

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 Loop of current-carrying wire

(armature) spins continuously(armature) spins continuously

Electric Electric MotorMotor

Parts of a MotorParts of a Motor

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

Brushes andcommutator

CommutaCommutatortor

Parts of a MotorParts of a Motor

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

BrushesBrushes

Brushes andcommutator

Parts of a MotorParts of a Motor

wires wires wrapped wrapped around around iron coreiron core

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 washer The washer The dryer The dryer The electric screwdriver The electric 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: