Magnetic and Electric Forces

Electric Charge and ForcesUnlike charges attract (+ and -) Like charges repel (- and -) (+ and +) The electric force depends on the charge

and distance. the electric force decreases as the distance

between them increases. as the amount of charge on either object

increases, the electric force between objects also increases.

Electric Fieldan electric charge is surrounded by an

invisible, electric field that exerts a force on other electric charges.

every proton and electron is surrounded by an electric field.

•The electric field around a positive charge points away from the charge. •The electric field around a negative charge points toward the charge.

Charging by Contactthe transfer of electric charge between objects

in contact.

example: As clothes tumble in a dryer, they rub against

each other. Charging by contact occurs and electrons are transferred from one article of clothing to another. This can cause articles of clothing to stick together

Charging by Inductionthe rearrangement of an electric charge due to

the presence of an electric field.

example: If you rub a balloon against your hair and then

stick the balloon to the wall. The electric field around the balloon repels the electrons in the wall. The electrons are pulled away from their atoms. This causes the wall close to the balloon to become positively charged. Which is why the negatively charged balloon is attracted to the positively charged wall.

insulators- materials in which electric charges do not move easily.

The electrons are held by atoms tightly.example: plastics, rubber, glass, and wood conductors - materials in which electric

charges can move easily. The electrons are held loosely by atoms. example: gold, silver, and copper Electrons can move easily through copper,

which is why it is widely used in electric wires.

static charge - the imbalance of an electric charge on an object.

example: if you walk across a carpet wearing shoes with rubber soles, charging by contact occurs.

Electrons are transferred from the atoms in the carpet to the atoms on the soles of your shoes.

When charging by contact occurs, the amount of positive and negative charge on each object is no longer balanced.

electric discharge - the movement of static charge from one place to another.

example: when you walk across a carpet and then touch a metal doorknob, you might feel an electric shock. There may be a spark. The spark is the electric discharge.

Can anyone think of another example?

The magnetic force between magnetic poles are attractive between unlike poles and repulsive between like poles.

Magnetic materialsIronNickelPaper clips (contains iron which is why it is

magnetic)

Distance and DisplacementDistance is the length of a path between

two points.

Displacement is the distance and direction between starting and ending points.