Electricity Notes

Electrical charge and static electricity

Atoms are made of charges, protons (+) and electrons (-). These charges exert forces. They push (repel) and pull (attract)).

Law of electrical charges: like charges repel (push apart) and unlike charges attract (pull toward each other).

http://www.youtube.com/watch?v=Y-5LxwZCfW4

Electric field is the location around ONE charge that would affect another charge within it.

Electric force is the push or pull between two charges.The amount of the force is based on the size of the charges and the distance.

(1) ATTRACT OR (2) REPEL

a. Two positive chargesb. Two negative chargesc. A negative and a positive charged. + -e. + +f. - -

Charge it!

Atoms usually are neutral (no charge) because they have an equal number of protons and electrons which cancel each other out.

However, atoms can lose electrons and become positively charged. (Only electrons move, not protons or neutrons)

a. Electric fieldb. Electric forcec. Neutral charged. Positive chargee. Negative charge

1

4

2.3

5.

How to charge an objectThere are three ways to charge an object.1)Friction – rubbing two things together results

in electrons moving from one object to the other.

2)Conduction – transfer of electrons by touch (similar to thermal conduction)

3)Induction – a negatively charged object approaches a neutral object making all the negative particles push away

http://phet.colorado.edu/simulations/sims.php?sim=Balloons_and_Static_Electricity

How do we know something is charged?

An electroscope shows whether something is charged by drawing the same charges from the metal and making the metal leaves spread apart.

(1) Conduction (2) Friction (3) Induction

A

B

C

Charging an object by rubbing it against another object so that electrons move from one to the other

Charging an object by touching to another object so that electrons transfer.

Bringing a charged object near an uncharged object so that the like charges are repelled and the uncharged object becomes charged.

(1) Conduction (2) Friction (3) Induction

A

B

C

Moving charges

Some materials conduct electricity meaning they allow charges to move easily through them, these are called conductors. - Conductors are used for wires. - Water is a conductor (unless it is distilled)- We also have to guard against materials that will allow electricity to flow through them if it isn’t something we want.

Insulators are materials in which charges cannot easily move. Such as:

- Plastic- Rubber- Wood- Glass- Air

(1) Conductor or (2) Insulator

1) Plastic water bottle2) Metal hinge3) Basketball4) Lead5) Stapler6) Wooden pencil7) Paper airplane

(1) Conductor or (2) Insulator

A Bc

D E

Static Electricity

Static electricity is the buildup of charges on an object. It is called static because it is not moving.

Electric discharge – eventually static electricity leaves an object. We call this electric discharge. It can occur slowly or quickly, as in electrical shock.

http://phet.colorado.edu/simulations/sims.php?sim=John_Travoltage

A cell is a device that produces an electric current by converting chemical energy into electrical energy. A battery is made of several cells. Batteries use DC or direct current which moves in one direction.

Photocells is the part of a solar panel that converts light into electrical energy.

A. Static electricityB. Electrical dischargeC. CellD. Photocell

1. Converts chemical energy into electrical energy2. Electric shock- when charges leave one object for

another less charged object3. The build up of charges on an object4. Converts light energy into electrical energy

Electric current

Current is the rate at which charges pass a certain point.

Our homes use AC or alternating current where the charges continually switch from one direction to the other. Voltage may vary. In the US we use 120V

Resistance

Resistance is the opposition to the flow of electrical charge. It is a type of “electrical friction“.

RESULTS IN HEAT!

A. Electric currentB. Static electricityC. Resistance

1. The result when charges build up but do not move.

2. The result when charges are opposed (slow down)

3. The result when charges move pass a certain point