Electricity & Magnetism

Electricity & Magnetism Static, Currents, Circuits Magnetic Fields & Electro Magnets Motors & Generators

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. • When static electricity is discharged a “spark” or “shock” occurs.

Static Discharge… • 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)

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

Conductors vs. Insulators • Conductors – material through which electric current flows easily. • A switch is a conductor that bridges the gap in a circuit • It is like a drawbridge- • When the bridge is down the people can pass- you have a closed circuit • When the bridge is up no one can pass- you have an open circuit • Insulators – materials through which electric current cannot move.

Conductors: Metal Water (only because of the minerals and metals in the water) Insulators: Styrofoam Rubber Plastic Paper Wood Examples

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

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

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

Parallel Circuit

How do we Measure Electricity? • Volt– the measurement of the amount of electrical push or force in a circuit • Watt– the measurement of power, or how fast work is done • Ampere– a unit used to measure how much current flows through a given part of a circuit in one second

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

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

Batteries • Batteries contain one or more electric cells • Electric cell- a wire connects 2 metals that are in contact with an electrolyte, it uses chemical energy to produce an electrical current • Electrolyte- a liquid or paste substance that conducts electricity

Batteries • Wet Cell- uses a liquid electrolyte to conduct electricity • Dry Cell- uses a paste electrolyte to conduct electricity • When a battery is “dead” it is because the metal in the battery no longer reacts with the electrolyte. • The electrolyte may be depleted or • The metal is used up

Magnetism • Magnetic Attraction- magnetic force, like charges repel, opposites attract • Magnetic Field- the area surround the magnet where the magnet’s force is expressed • Strongest at the poles

Electricity and Magnetism • These are very closely related • Like charges repel • Opposites attract • The flow of electricity can produce a magnet, and a magnet can produce electricity

What is an electromagnet? • Electromagnet – a magnet made from a coil of wire wrapped around an iron or steel core that is attached to a electrical source.

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

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

Electronics • Electronic Device- an object that uses electricity to communicate information. • Electronic devices use an electrical signal which is an electrical current that carries information • TV, Cell phone, iPod….. Etc • These electronic devices use a binary number system (BNS) to communicate • BNS- a code using a series of numbers • 0 is an open circuit, 1 is a closed circuit

Integrated Circuits • Integrated Circuit- a computer chip or microchip, a small circuit with all the parts built into it. • Semi-conductor- a material that somewhat conducts electricity, conducts better than an insulator but not as well as a conductor • Acts similar to a switch can act like a conductor, closed circuit and or resistor • silicon

Computer Parts • CPU- central processing unit, it is the brain of the computer, it tell the rest of the computer what to do • ROM- read only memory- built in memory and programs- it is the instructions • RAM- random access memory- store information temporarily

That’s It !!!!

Electricity & Magnetism