Jag MarkHow do like charges interact? unlike

charges?

Electric Charge and

Static Electricity

Notes

Electric Charge

•Electric charge is a property of protons and electrons.

•Protons have a positive charge. Electrons have a negative charge.

ProtonElectro

n

Electric Charge•Two charges that are the same push away

from each other. Two charges that are different pull toward each other.

•If a proton and an electron come close together, they attract each other.

•Attraction (pull) and repulsion (push) between electric charges is known as interaction between charges. The interaction between charges is called electricity.

Repulsion Attraction

Electric Charge•This is different from the

interaction between magnetic poles, which is known as magnetism.

•The terms “positive” and “negative” were given to charges by Benjamin Franklin in the 1700s.

Electric Charge

•Balloon + Aluminum Can

•Comb + Paper

•Balloon + Water

Electric Force•Electric force is the attraction or

repulsion between electric charges.

•A magnetic field surrounds a charged object. An electric field is a region around a charged object in which electric force occurs.

Electric Force•Suppose one charged object is placed in

the electric field of a second charged object. The first charged object is either pushed or pulled -- repelled or attracted.

•The strength of an electric field depends on how far away the charged object is. The farther away a charged object is, the weaker the electric field is.

The strength of an electric field is represented by how close the electric field lines are to each

other.

Static Electricity•Most objects usually have no charge.

However, objects can become charged.

•If an object loses electrons, it has more protons than electrons. Therefore, it has a positive charge.

•If an object gains electrons, it has more electrons than protons. Therefore is has a negative charge.

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Before Rubbing(uncharged)

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After Rubbing(Negatively Charged)

•Static Electricity is the buildup of charges on an object. Static means “not moving.” In static electricity, the charges do not flow or move.

Static Electricity

Transferring Charge•An object becomes charged when

electrons move from one place to another place.

•Charging by friction is when electrons move from one uncharged object to another object by rubbing. For example, a girl charges by friction when she runs her socks on the carpet.

Transferring Charge•Charging by conduction is when

electrons move from a charged object to another object by direct contact. You can charge yourself by conduction when you touch a charged object.

•Think: carpet > socks = friction

•Then: socks > feet = conduction

Transferring Charge

•Charging by induction is when electrons move to one part of an object due to the electric field of another object. There is no touching in charging by induction.

Transferring Charge

•You can find out if an object is charged by using an instrument called an electroscope.

When the object is uncharged, the leaves hang down, but if a charged object gets close, the leaves repel each other and

spread apart.

Static Discharge•Charges may build up as static

electricity on an object. But the charges do not stay on that object forever.

•The loss of static electricity as charges move from one object to another is called static discharge.

Static Discharge

•A static discharge often produces a spark. For example, there may be a tiny spark when you touch a metal doorknob. Lightning is another example of static discharge.