TOPIC 9 ELECTRICITY Atoms Have neutrons protons and

TOPIC 9 ELECTRICITY

Atoms • Have neutrons, protons, and electrons. • Protons are positively charged • Electrons are negatively charged

Electrons • Are located on the outer edges of atoms…they can be moved. • A concentration of electrons in an atom creates a net negative charge. • If electrons are stripped away, the atom becomes positively charged

The world is filled with electrical charges - - -

What is this electrical potential called? • Static Electricity

Static Electricity • The build up of an electric charge on the surface of an object. • The charge builds up but does not flow. • Static electricity is potential energy • It does not move • It is stored

Conservation of Charge • Conservation of Charge: Electrical charge can be transferred from one object to another but it cannot be created or destroyed • Sound Familiar?

When two objects rub against each other electrons transfer and build up on an object causing it to have a different charge from its surroundings. Like the shoes rubbing against the carpet. Electrons are transferred from the carpet to the shoes.

Static Discharge or Transfer of Charge • Occurs when there is a loss of static electricity due to three possible things: • Friction - rubbing • Conduction – direct contact • Induction – through an electrical field (not direct contact)

Conductors • Conductors are materials that allow electrons to move freely • We did a conduction lab • What material was a good conductor?

Insulators • Insulators are materials that don’t allow electrons to move freely • Energy takes a lot longer to transfer • Think of the conduction lab again, which of the materials was the insulator? • The plastic coating around metal wires prevents electrical charge when you touch it

Charging Objects • Charges can transfer from one object to the next just by touching • This is called charging by contact • Better known as friction • Charging by induction is the use of an electrical field instead of an object to transfer charge

• John Travoltage - Voltage, Static Electricity, Electricity – Ph. ET • NOVA (PBS) - Lightning! (1995) – You. Tube • Lightning Strikes! - You. Tube

Electricity that moves… l Current: The flow of electrons from one place to another. l Measured in amperes (amps) l Kinetic energy

There are 2 types of currents: l Direct Current (DC) – Where electrons flow in the same direction in a wire.

There are 2 types of currents: l Alternating Current (AC) – electrons flow in different directions in a wire

How can we control currents? l With circuits l Circuit: is a path for the flow of electrons l We use wires

There are 2 types of circuits: l Series Circuit: the components are lined up along one path. If the circuit is broken, all components turn off.

Series Circuit

There are 2 types of circuits: l Parallel Circuit – there are several branching paths to the components. l If the circuit is broken at any one branch, only the components on that branch will turn off.

Parallel Circuit

What is Resistance? l The opposition to the flow of an electric current, producing heat. l The greater the resistance, the less current gets through. l Good conductors have low resistance. l Measured in ohms.

What is Voltage? l The measure of energy given to the charge flowing in a circuit. l The greater the voltage, the greater the force or “pressure” that drives the charge through the circuit.

Difference b/t Volts and Amps l Example l Amps – you could say that… measure how much water comes out of a hose. l Volts measure how hard the water comes out of a hose.

Ohm’s Law l Resistance l Ohms = Voltage / Current = Volts / Amps

Ohms Triangle

Practice with Ohm’s Law Ohms 4 15 2 9 6 Volts 100 150 30 45 48 Amps 25 10 15 5 8

What is an electromagnet? l Electromagnet – a magnet made from a current bearing coil of wire wrapped around an iron or steel core.

What is a generator? l Generator – a machine that changes mechanical energy to electrical energy l Usually use moving magnets to create currents in coils of wire.

What is a motor? l Motor – a device that changes electrical energy to mechanical energy that can do work.

What is a battery A battery provides the needed voltage to keep a current flowing in a circuit l There are two types of batteries: l l Dry Cell: most common (AAA, AA) two electrodes surrounded by material called electrolytes l Wet Cell: (Car battery), Plates of metal of different compounds in a conducting solutions a wet cell battery is many of these cells put together