SCI.8.3.6.1Explain the electrical nature of matter. May use simulations. SCI.8.3.6.3Compare and contrast conductors and insulators. Provide examples of.

SCI.8.3.6.1 Explain the electrical nature of matter. May use simulations. SCI.8.3.6.3 Compare and contrast conductors and insulators. Provide examples of materials that are good conductors,

semiconductors, and insulators. SCI.8.3.6.4 Differentiate between current and static electricity.  SCI.8.3.6.5 Describe the properties of magnets and explain the relationship between a magnetic field and an electric

current. SCI.8.3.6.6 Compare and contrast generators and motors and how they function including induction and grounding. SCI.8.3.6.7 Identify situations in everyday life where motors and generators are in use. SCI.8.3.6.8 Construct and compare simple, series, and parallel circuits to determine the relationship between current,

voltage, and resistance. SCI.8.3.6.12 Show the relationship between resistance, voltage, and amperage (Ohm’s Law) when solving simple circuit

problems. SCI.8.1.1.18 Design an investigation to illustrate the effects of static electricity. SCI.8.3.6.10 Create an electromagnet, explain how it works, and know the factors that affect the strength of

electromagnets.  SCI.8.3.6.11 Solve simple current problems using Ohm’s law. NEW Explain how diodes and transistors work.

Electric Charge

Protons and electrons both have the property of charge. Recall that protons are positive and electrons are negative.

A force of attraction exists between things that have opposite charges.

A force of repulsion exists between things that have same charges.

Electric Field

An electric field extends outward through space from every charged particle. As things move toward each other the charge may move from one object to another.

The electric field is strongest near the charged particle.

Static Electricity

Because electrons can move freely things can become either positively or negatively charged.

Charge is only being transferred from one object to another. This is called the Law of Conservation of Charge.

Static electricity – is the buildup of electric charges on an object.

Methods of Charging

Friction – when two objects are rubbed together. Example: balloon on your hair.

Conduction – the direct contact of objects. Example: plugging something in. Conductors – allow electricity to go through easily Insulators – do not allow it to move through.

Induction – the jumping of electricity from one object to another. Example: a negatively charged rubber rod can pick up tiny pieces of paper.

Generators and Motors a generator  converts mechanical energy into

electrical energy.

electrical motor, which converts electrical energy into mechanical energy.

Both motors and generators run because of something called electromagnetic induction. Discovered by Michael Faraday, this is when a voltage is induced by a changing magnetic field. With electromagnetic induction, an electric current can be produced in a coil of wire by moving a magnet in or out of that coil, or by moving the coil through the magnetic field. Either way, voltage is created through motion.

Comparing Generators and Motors

* They both rely on the principle of electromagnetic in induction. * The both contain coils of wire magnets or electromagnets and they both have rotating parts. * The AC generator will probably work as an AC motor and the DC motor will probably work as a DC generator. * The AC generator will turn rotational energy into electrical energy with an alternating current (AC). That is, the current will vary in the shape of a sine wave above and below zero amps. * The DC motor will turn electrical energy from a direct current (DC) source into rotational energy. * The AC generator may generate more than one electrical phase. That is, it might work like more than one generator at a time.

Electric Discharge

Electric discharge – the

loss of static electricity as

electric charges move off

an object. Sometimes

slow and quiet, or rapid

with a spark of light, shock,

or crackle of noise.

Example: lightning or a

simple static shock

Circuits

A circuit – is formed when a wire is connected to the terminals of a source forming a complete path.

Electric current – the amount of charge that passes a given point per unit of time.

The symbol for current is I

Things to know… Georg Simon Ohm

established the relationship between electric current and potential difference. Ex. 8 v battery vs 4 v battery.

Resistance – R opposition to the flow of electric charge (example: copper low: iron high) The unit to measure resistance is the ohm

Ohm’s law – the current in a wire is equal to the voltage divided by resistance

I = V/R

Superconductor

Superconductor – low temperatures, resistance is zero. Must be kept extremely cold.

A phenomenon observed in several metals. When these materials are cooled to temperatures near absolute zero, using liquid nitrogen, they have no electrical resistance. This means they can carry large amounts of electrical current for long periods of time without losing energy as heat.

Superconducting loops of wire have been shown to carry electrical currents for several years with no measurable loss

Another property of a superconductor is that magnetic fields can't penetrate it. It has implications for making high speed, magnetically-levitated trains… kinda neat huh…

Current direction

DC (direct current) – electrons always flow in the same direction. Example: batteries

AC (alternating current) electrons move back and forth, reversing direction regularly. (example: current in home changes direction every second 120x)

Diodes A diode allows electricity to flow in one direction

only and blocks the flow in the opposite direction. They may be regarded as one-way valves and they are used in various circuits, usually as a form of protection.

Transistors A transistor is a miniature electronic component that

can do two different jobs. It can work either as an amplifier or a switch: When it works as an amplifier, it takes in a tiny electric current at one end (an input current) and produces a much bigger electric current (an output current) at the other. In other words, it's a kind of current booster -  hearing aid

Transistors can also work as switches. A tiny electric current flowing through one part of a transistor can make a much bigger current flow through another part of it. In other words, the small current switches on the larger one. This is essentially how all computer chips work. For example, a memory chip contains hundreds of millions or even billions of transistors, each of which can be switched on or off individually.

CircuitsElectric circuit –

consists of a source of energy; a load; wires, and a switch.

Sources: battery, thermocouple, photocell, or electric generator

Load – uses the electricity

switch

source

loadwire

Series vs Parallel

Series circuit – only one path to take; if any part goes out the whole thing goes out. Example: old Christmas lights

Parallel circuit – separate paths. Example: circuits in homes. Fuses – protect against too much current flow, they burn out and

can be a hassle Circuit breakers – like fuses but do not burn out. Take out packet & complete page 2 Electrical Currents

Series vs Parallel

Power

Electric Power – a measure of the rate at which electricity does work or provides energy. Measured in watts.

Power = voltage x current

Energy = power x time

Electric Safety Never handle when wet or near water

Never run wires under carpet

Never overload circuits

Repair worn out wires

Put nothing in electric sockets that does not belong

Never go by fallen wires or power lines

In lightning storms get down to the ground by crouching down and stay away from trees.

Safest spot in a lightning storm is inside a car.