Basic Electricity DC and AC

What is Electricity? Electricity is a general term used for the presence and flow of electric charge. Electricity is a general term used for the presence and flow of electric charge.electric chargeelectric charge In more scientific terms, it is the flow of electrons from one place to another. In more scientific terms, it is the flow of electrons from one place to another.

Types of Electricity Static – Metal door handles on cold dry mornings (OUCH!) Static – Metal door handles on cold dry mornings (OUCH!) Stored – Batteries, etc. Stored – Batteries, etc. Generated- Provides our homes and schools with power. Generated- Provides our homes and schools with power. All deal with the flow of electrons from one point to another. All deal with the flow of electrons from one point to another.

Electrons? As we know, an atom is made up of sub- particles, those being: As we know, an atom is made up of sub- particles, those being: ELECTRONS (negatively charged) ELECTRONS (negatively charged) PROTONS (positively charged) PROTONS (positively charged) NEUTRONS (neutral, no charge) NEUTRONS (neutral, no charge)

ELECTRON (-) PROTONS (+) & NEUTRONS (0)

Electron Flow To illustrate the most basic form of electron flow, we use something called a circuit. To illustrate the most basic form of electron flow, we use something called a circuit. The circuit is made up of a power source, conductors (wires) to provide a path for the electrons to flow, and a useful device such as a light bulb (also called a LOAD) The circuit is made up of a power source, conductors (wires) to provide a path for the electrons to flow, and a useful device such as a light bulb (also called a LOAD)

The Basic Circuit NEGATIVE ( - ) POSITIVE (+) Electrons flow NEGATIVE to POSITIVE

The Circuit Shown Here is a DC (Direct Current) Circuit In a DC Circuit, there is only ONE direction for current flow. Note the switch opens, current stops flowing.

DC Circuits Direct Current is provided to us mostly by batteries, used in : – Flashlights – iPods – Laptop Computers – Automobiles – Solar Cells

DC Series Circuits Loading batteries in a flashlight is a good example. Batteries are placed end to end, positive to negative __ _ 1.5 volts

Batteries in Series When batteries are installed this way, they are said to be AIDING one another. If three 1.5 volts batteries were installed in a flashlight, what would the total voltage be ? 3 X 1.5 = 4.5 volts

Parallel If batteries are connected in parallel, something completely different happens. A good example of this is connecting jumper cables between car batteries. A car battery is 12 volts. If the cables were hooked up in SERIES, = 24 volts, and the starter would be TOAST!

Parallel Circuits Instead, Positive is connected to Positive. Negative is then connected to Negative. The voltage remains at 12 volts – it does not increase. What DOES increase is the amount of electrical current to turn over a weak starter.

Series vs. Parallel Each have their use SERIES increases voltage (add voltages) PARALLEL increases current.

SERIES- 3 bulbs drop 4 volts each to divide the load. 3 times 4 = 12. SERIES- 3 bulbs drop 4 volts each to divide the load. 3 times 4 = 12. PARALLEL – 12 volts is present EVERYWHERE in the circuit WHAT IF A BULB GOES OUT IN EITHER SITUATION? WHAT WILL HAPPEN TO THE OTHER BULBS?

AC Current A more complicated type of current is AC, or Alternating Current. A more complicated type of current is AC, or Alternating Current. Like DC, it involves the movement of electrons. Like DC, it involves the movement of electrons. Unlike DC, AC electrons move in one direction, then they reverse. Unlike DC, AC electrons move in one direction, then they reverse. This means that current flows one way, then the other. This means that current flows one way, then the other.

AC AC power is provided to us by our electric company. AC power is provided to us by our electric company. Without it, life would be rather dull (and DARK) Without it, life would be rather dull (and DARK) AC powers just about everything in our homes that use electricity. AC powers just about everything in our homes that use electricity. When you plug a power cord into a wall outlet, you are using AC. When you plug a power cord into a wall outlet, you are using AC.

AC – Alternating Current AC is created by a device called a generator (or ALTERNATOR) As a result of magnetic field being cut by a conductor, AC is produced. AC in its simplest form is represented by something called a SINE WAVE…….

The AC Sine Wave How The Sine Wave Is Produced

The SINE WAVE This drawing represents how a sine wave looks when viewed through an oscilloscope 0 dg 90 dg 180 dg 270 dg 360 dg180

Producing AC Sine Waves

Basic Generator

0 degrees

90 degrees

180 degrees

270 degrees

360 degrees

BECAUSE OF ITS VERSATILITY AC IS EASIER TO GENERATE AC IS EASIER TO TRANSMIT AC IS EASIER TO STEP-UP OR DOWN AC IS MORE ECONOMICAL WHY AC ?

Producing AC AC GENERATING STATIONS USE A VARIETY OF METHODS TO PRODUCE ELECTRICITY AC GENERATING STATIONS USE A VARIETY OF METHODS TO PRODUCE ELECTRICITY HYDROELECTRIC HYDROELECTRIC STEAM STEAM COAL COAL NUCLEAR…..ARE MEANS OF OPERATING THE TURBINES THAT PRODUCE THE ELECTRICITY NUCLEAR…..ARE MEANS OF OPERATING THE TURBINES THAT PRODUCE THE ELECTRICITY

Generating AC THE VOLTAGE THAT LEAVES THE GENERATING STATION IS VERY HIGH THE VOLTAGE THAT LEAVES THE GENERATING STATION IS VERY HIGH APPROX. 275,000 VOLTS OR MORE APPROX. 275,000 VOLTS OR MORE THE ELECTRICITY MUST BE STEPPED DOWN BEFORE POWERING OUR HOMES THE ELECTRICITY MUST BE STEPPED DOWN BEFORE POWERING OUR HOMES HOUSEHOLD CURRENT IS 120/240 VOLTS AT 60 HERTZ HOUSEHOLD CURRENT IS 120/240 VOLTS AT 60 HERTZ TRANSFORMERS ARE USED TO STEP DOWN VOLTAGE FROM HIGH TO LOW TRANSFORMERS ARE USED TO STEP DOWN VOLTAGE FROM HIGH TO LOW

Transformers

Other AC Uses AC IS USED IN TELECOMMUNICATIONS AC IS USED IN TELECOMMUNICATIONS AC SIGNALS ALLOW INTELLIGENCE TO BE XMITTED OVER LONG DISTANCES AC SIGNALS ALLOW INTELLIGENCE TO BE XMITTED OVER LONG DISTANCES A XMITTING ANTENNA CONVERTS AC SIGNALS INTO ELECTROMAGNETIC WAVES A XMITTING ANTENNA CONVERTS AC SIGNALS INTO ELECTROMAGNETIC WAVES THE SIGNAL THAT REACHES RADIOS AND TV’S IS AC THE SIGNAL THAT REACHES RADIOS AND TV’S IS AC

More About AC AC is not only measured in VOLTS, but also in a unit called the HERTZ. AC is not only measured in VOLTS, but also in a unit called the HERTZ. The HERTZ is a unit of measuring time, called FREQUENCY. The HERTZ is a unit of measuring time, called FREQUENCY. The electricity in our houses makes 60 complete cycles per second, therefore its frequency is 60 HERTZ. The electricity in our houses makes 60 complete cycles per second, therefore its frequency is 60 HERTZ.

More Uses for AC Sometimes AC power is all that is available, but you have a device such as a music player that operates on batteries. Sometimes AC power is all that is available, but you have a device such as a music player that operates on batteries. What do you do ?????????????? What do you do ??????????????

Converting AC to DC By using a Power Supply, the AC wave is cut in half and filtered so that it becomes smooth DC. By using a Power Supply, the AC wave is cut in half and filtered so that it becomes smooth DC. AC adapters perform this task. AC adapters perform this task. 120 VAC 12 VAC 12 V DC

SAFETY FIRST ! When working around electricity, one must observe some basic precautions: When working around electricity, one must observe some basic precautions: Never work with electricity when wet. Never work with electricity when wet. Be careful that metal objects or liquids don’t come in contact with electricity. Be careful that metal objects or liquids don’t come in contact with electricity. NEVER pour water on an electrical fire!! NEVER pour water on an electrical fire!! Try to use only one hand if at all possible. Try to use only one hand if at all possible. Electricity is something we can’t see (but can sure feel if we goof up!) Electricity is something we can’t see (but can sure feel if we goof up!)

What did we learn? What is the difference between AC and DC? What is the difference between AC and DC? What is the difference between a SERIES and a PARALLEL circuit ? What is the difference between a SERIES and a PARALLEL circuit ? What is a common household voltage? What is a common household voltage? What is the basic AC wave called? What is the basic AC wave called?

The End