Static Electricity

• Electrostatics is the study of electrical charges at rest.

What makes electrical charges?

Protons and electrons

What type of charge do protons have? Where are protons located in an atom?

Protons are positively charged. They are located in the nucleus of an atom.

What type of charge do neutrons have? Where are neutrons located in an atom?

Neutrons are neutrally charged (have no charge) and are located in the nucleus of an atom.

What type of charge do electrons have? Where are they located in an atom?

Electrons are negatively charged and orbit the nucleus of an atom.

• All charged particles exert forces on one another.

If you put two like charges next to one another (i.e. a proton and a proton), what will they do?

They will repel.

If you put two opposite charges next to one another, what will they do?

They will attract.

If you put two neutrons next to one another, what will they do?

Nothing.

If an atom is neutrally charged, what must be true about the number of protons and electrons?

A neutral atom has an equal number of protons and electrons.

What is an atom with an unequal number of protons and electrons called?

• An atom with an unequal number of protons and electrons is called an ion.

If an atom is a positive ion and it has 6 protons, how many electrons could the atom have?

The atom must have more protons than electrons if it is a positive ion, therefore it could have 0-5 electrons.

How does something become a positive ion? Does it gain a proton or does it lose an electron or could it do both?

It must have lost an electron.

• Protons cannot be removed from atoms because they are held tightly in the nucleus.

• Electrons can be transferred from one atom to another.

If a balloon is rubbed with a piece of fur and placed near some bits of paper, the paper will jump onto the balloon.

The balloon doesn’t even need to touch the bits of paper for this to work.

• Any charged object can exert this force upon other objects - both charged and uncharged objects.

• This is known as the electric force.

• The electric force is a field force. This means the objects do not have to touch for there to be a force between them.

Can you think of any other field forces?

• Electrical charges have force fields surrounding them. They are called electric fields.

• The closer you are to an electric charge, the stronger the electric field becomes.

Can a neutrally charged object and a charged object attract?

YES!!!

How can a neutrally charged and a charged object attract?

• When a charged object is placed near a neutral object, charges within the neutral object become polarized.

The behavior of a charged object greatly depends on what the object is made of.

• A conductor is a material which permits electrons to flow freely from atom to atom and molecule to molecule.

• An insulator is a material that impedes the free flow of electrons from atom to atom and molecule to molecule.

We learned last semester that an object that is held off the ground has gravitational potenital energy. If the object were let go, it would fall to the Earth because of the Earth’s gravitational force.

• When two charged particles are held a distance apart from one another, there exists electrical potential energy between them.

If you hold two protons near each other and let go, they will move apart.

If you hold and electron and a proton near each other and let

go, they will move together.

Electrical potential energy can be transferred to kinetic energy.

• Electric potential is measured in units of volts.

Where have you seen the unit volt before?

A volt is the unit for a battery. A battery pushes electric charges around a circuit. The electric charges running around the circuit is called current. So voltage is the energy a battery provides to the electrons in the wires of a circuit.

The terms volt and voltage can be used interchangeably.

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