Electrical Charge

Ever been shocked?

Electrical ChargeWhat were you doing when

it happened?

Electrical ChargeMaybe you:

Were getting clothes out of the dryer

Were grabbing a metal door knob

Rubbed your socks on the carpet and then ran and

touched your mom…

Or you pet this dog….

Electrical Charge•All material objects are composed of atoms

•Let’s review the atom…

Electrical Charge•There is a nucleus and a lot of space outside the nucleus•The nucleus is composed of protons and neutrons•The space outside the nucleus contains electrons

Electrical Charge•Protons have a positive (+) charge•Neutrons have NO charge

or are neutral•Electrons have a negative (-) charge

Electric Charge

Electrical ChargeThe mass of an atom is mostlyin the nucleus because protons and neutrons are much heavier than electrons

Electrical Charge

Electrical ChargeIf the nucleus contains protons (+), and like charges repel, how

does the nucleus stay intact?

Static Electricity

When enough neutrons are present the strong nuclear force wins out over the repulsion between positively charged protons and pulls the nucleus together tightly. The strong nuclear force is the strongest force in the universe that we know.

Electrical ChargeWhat keeps the nucleus bound

together? How?

Electrical ChargeStrong nuclear force - This force attracts neutrons and protons to each other and works only at extremely small distances.

Electrical ChargeStrong nuclear force is the strongest force in the universe that we know.

Electrical ChargeWhat force keeps

electrons bound to an atom? Why don’t the fall to the nucleus?

Electrical ChargeElectromagnetic Force – the force that binds electrons to the nucleus. It is the attraction between the positive charge on protons and the negative chargeon electrons.

The electrons don’t fall into the nucleus because they have momentum. The momentum of an electron causes it to move around the nucleus instead of falling. A good analogy is Earth orbiting the sun. Gravity creates a force that pulls Earth toward the sun. Earth’s momentum causes it to orbit the sun rather than fall straight in.

Electrical Charge•Protons and neutrons in the nucleus are not easily removed or disturbed.•Electrons are weakly bound to the atom

Electrical Charge•Because electrons (-) are weakly bound to the atom, they are often removed from one atom and added to another one by normal everyday events.

Electrical ChargeStatic Electricity is any imbalance in either positive or negative charge on an object.

Electrical ChargeElectric charge, like mass, is a

fundamental property of matter.

(All matter has mass; all matter has electric charge.)

•There are two types of charges•Positive (+)•Negative (-)

Electrical ChargeThe unit of charge is the coulomb, CNamed after French Physicist Charles Augustin de Coulomb (1736-1806), who performed the first accurate measurements of the force between charges.

Electrical Charge•Most matter is Neutral, it has NO charge, the (+) and (-) charges are equal

An object with a net charge of zero is described as being electrically neutral.

Your pencil, your textbook, even your body are electrically neutral (at least most of the time).

Electrical Charge•If an object gains or loses one kind of charge, it is charged

If you have ever felt a shock when you have touched a doorknob or removed clothes from a dryer, you have experienced a charged object.

An object is charged when its net charge is not zero.

A tiny imbalance in either positive or negative charge on an object is the cause of static electricity.

If two neutral objects are rubbed together, the friction often pulls some electrons off one object and puts them temporarily on the other.

Static Electricity is the build up of charge on an

object or material

1. A positively charged pop can is touched by a person standing on the ground. The pop can subsequently becomes neutral. The pop can becomes neutral during this process because ______.a. electrons pass from the pop can to the person (ground) b. electrons pass from the person (ground) to the pop canc. protons pass from the pop can to the person (ground)d. protons pass from the person (ground) to the pop can 2. A physics student, standing on the ground, touches an a negatively charged electroscope. This will cause ___.a. the electroscope to be grounded as electrons flow out of the electroscope. b. the electroscope to be grounded as electrons flow into the electroscope.c. the electroscope to be grounded as protons flow out of the electroscope.d. the electroscope to be grounded as protons flow into the electroscope.

3. TRUE or FALSE:An object that becomes grounded gains neutrons during the grounding process.

Electrical ChargeIf you rub a balloon on your hair, you can make it stick to a wall.When the balloon and your hair are rubbed together, electrons are transferred from your hair to the balloon. This is called charging byfriction.

Electrical ChargeCharging by friction – when

two neutral objects are rubbed together and charge is

transferred causing the objects to become oppositely charged.

Electrical ChargeWhen the balloon is brought near the wall, electrons inside atoms near the wall’s surface are slightly repelled toward the far side of the atom. The wall’s atoms become polarized — one end positive, the other negative

Electrical Charge

Electrical Charge

https://phet.colorado.edu/en/simulation/balloons

Electrical ChargeExplain the difference between an electrically charged and a neutral

object.

Electrical ChargeExplain how there can be

charge inside matter yet the matter is electrically

neutral.

Coulomb’s LawThe force between charges is very strong

Coulomb’s LawThe force between two objects depends on two things:-the charge -the distance

Coulomb’s LawMore charge = more force

More distance = less force

(Hmm.. This reminds me of universal gravitation…)

Coulomb’s Law

The force between charges is directly proportional to the magnitude (the amount) of each charge.

The force between charges is inversely proportional to the square of the distance between them. (This relationship is called the inverse square law.)

You are about to do practice problems on your own paper.

You may do them within your notes.

I will come by and stamp your answers at the end of each problem

Two steel marbles are each given a net charge of one thousandth (0.001) of a coulomb.Calculate the size of the force on the marbles if they are held 2 meters apart.

Everyone try this problem

Calculate the size of the force if the marbles are held 4 m apart

Calculate the size of the force between 3 C and 4 C charges 500 m apart.

Calculate the size of the force between 2 C and 4 C charges 300 m apart.

ANSWERS….

1. 2,250 N2. 562.5 N3. 432,000 N4. 800,000 N