Intro to Electricity

During this PowerPoint, take GOOD CORNELL notes During this PowerPoint, take GOOD CORNELL notes! I will not create notes to share with you, though this PowerPoint will remain online, so take GOOD notes. There will be a Exit Pass at the end of class today….you can use YOUR notes, so take GOOD ones!

It all starts with the atom…what doesn’t? Everything in the world is made up of atoms. Each atom has subatomic particles (smaller parts). For now, we will only look at the THREE main types of subatomic particles; Protons (+), Neutrons (N), and Electrons (-).

Protons (+) and Neutrons (N) make up the nucleus (Center of the Atom) Protons (+) and Neutrons (N) make up the nucleus (Center of the Atom). The electrons, who are MUCH MUCH smaller particles move quickly around the nucleus.

Some electrons, since they are SO small, can jump from atom to atom easily (called FREE electrons). When an electron moves to a different atom, it creates an imbalance (a charge). This also creates a need for the atom to try to stabilize = Electricity (in some shape or form)

Electrons (-) are attracted to protons (+). OPPOSITES attract Electrons (-) are attracted to protons (+). OPPOSITES attract. If an atom GAINS an electron (-) it is now NEGATIVELY charged. It is now an ION (an ANION to be exact!) The atom that lost an electron (-) is now POSITIVELY charged. It is now an ION (a CATION to be exact!) A charge is a measure of the extra positive or negative particles that an object has.

The steady flow of electricity is called an electric current The steady flow of electricity is called an electric current. A current will move along a wire or a path called a circuit. Circuit means to “go around.” ELECTRIC CURRENT IS MEASURED IN AMPERES (AMPS)

Types of Electricity Static electricity--- The collection of electrons (anions) and positive ions (cations) on the surface of a material--usually an insulator (addressed later) like plastic, rubber, or glass Static electricity occurs because a “charge” that stays on an object until it balances or stabilizes! = ZAP!

Types of Electricity D/C –Direct current –The positive and negative terminals of a battery are always, respectively, positive ­and negative. Current always flows in the same direction between those two terminals. A/C –Alternating current –The direction of the current reverses, or alternates, 60 times per second (in the U.S.) or 50 times per second (in Europe). The power that is available at a wall socket in the United States is 120-volt, 60-cycle AC power.

A conductor is a material that current can pass through easily, like metals.

An insulator is a material that current cannot pass through easily: Plastic Rubber Glass Most metal oxides (like rust) Air Oil Pure, de-ionized water Insulator

The difference between the metals, conductors, and the insulators can be explained by looking at the number of free electrons in them.  Conductors have a large number of free electrons which can carry charges (they can move around easily), while insulators have practically no free electrons.   What is the difference?

A semiconductor is a material with an electrical conductivity that is between that of an insulator and a conductor.  In a process called doping, small amounts of impurities are added to pure semiconductors causing large changes in the conductivity of the material. Semiconductor

Importance of Semiconductors Semiconductors can be conductors as well as insulators. Temperature can alter their conductivity (Colder = More insultor-like). The combination of different semiconductors producess devices with special electrical properties, which allow control of electrical signals. For example, electronic devices use semiconductors. Without the discovery of semiconductors, there would be no radios, no TV's, no computers, no video games, and VERY poor medical diagnostic equipment. Importance of Semiconductors

Did you know that because silicon is an important element in semiconductor and high-tech devices, the high-tech region of Silicon Valley, California, is named after this element? Random Trivia!

A resistor is a material that resists, but doesn’t stop the flow of current.

Circuits A series circuit is a circuit that has only one path for the current. A parallel circuit has more than one path for current to travel.

Lights wired in a series circuit are all in the same loop…one goes out, the others go out! That is how Christmas Lights used to be wired….before they got smart!

Lights in our homes are wired in parallel circuits---If one goes out, the others stay lit!

Key Measures of Electricity (C) Coulomb-unit of measure for electric charges/current. *Not used often due to more widely accepted in electrical engineering is the amp. ( I ) Current is what flows on a wire or conductor like water flowing down a river. Current flows from negative to positive on the surface of a conductor. Current is measured in (A) amperes or amps. ( E ) Voltage is the difference in electrical potential between two points in a circuit. It's the push (FORCE) or pressure behind current flow through a circuit, and is measured in (V) volts. ( R ) Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. A very high resistance allows a small amount of current to flow. A very low resistance allows a large amount of current to flow. Resistance is measured in ohms. ( P ) Power is the amount of current times the voltage level at a given point measured in wattage or watts. OR The rate at which energy is transferred.

We’ll be working with Current, Voltage, and Resistance again, but let’s be SURE we understand what Power is. Power is the measurement of energy transfer over time, and energy costs money. Batteries aren’t free, and neither is that stuff coming out of your electrical outlet. So, power measures how fast the pennies are draining out of your wallet!

Let’s relate this back to ENERGY! Electric energy in particular, begins as electric potential energy – (This is voltage!). When electrons flow through that potential energy, it turns into electric energy (current). In most useful circuits, that electric energy transforms into some other form of energy. Electric power is measured by combining both how much electric energy is transferred, and how fast that transfer happens.

Watt (unit for Power) is measuring ENERGY! As you know, energy is measured in joules (J). Since power is a measure of energy over a set amount of time, we can measure it in joules per second. The metric (SI) unit for joules per second is the watt abbreviated as W. Watt (unit for Power) is measuring ENERGY!

*Taken from http://science.howstuffworks.com/electricity7.htm “If you know the amps and volts involved, you can determine the amount of electricity consumed, which we typically measure in watt-hours or kilowatt-hours. Imagine that you plug a space heater into a wall outlet. You measure the amount of current flowing from the wall outlet to the heater, and it comes out to 10 amps. That means that it is a 1,200-watt heater. If you multiply the volts by the amps, you get the wattage. In this case, 120 volts multiplied by 10 amps equals 1,200 watts. This holds true for any electrical appliance. If you plug in a light and it draws half an amp, it's a 60-watt light bulb.” *Taken from http://science.howstuffworks.com/electricity7.htm