Electricity The flow of charges

Atoms MMade up of: Nucleus: Protons and neutrons Electrons: negative charge orbit nucleus

Current  Flow of electrons Measured in Amperes (Amps)  Electrons passing per second

Circuit  Must have complete, unbroken path for current to flow 3 Parts: 1.Load: device run by electricity 2.Wires: path for electron flow 3.Source: moves the electrons through the wire Battery, generator, wall socket (power plant)

A break in the circuit stops electricity from flowing

Conductors  Materials allowing electrons to flow Examples:  metals: electrons loosely held, move easily Copper is one of the best

Insulators  Do not allow electricity to flow Examples: rubber, plastic  Electrons held tightly, will not move easily

Voltage  Measures the force “pushing” electrons Volt (v) as unit  Higher voltage is higher potential to push electrons through circuit

WWater dam Lower Potential energy =Low voltage Higher Potential energy=high voltage

Resistance  Force working against (“resisting”) the flow of electrons Measured in Ohms (Ω) All parts of circuit “slows the flow”

Ohm’s Law  Tells how current, voltage, resistance are related Current = voltage resistance I = V R

Practice Ohm’s Law AA 9 volt battery is used to light 3 bulbs with a resistance of 0.5 Ω each. Wires and a switch add another 3 ohms of resistance. How much current (amps) is flowing through the circuit? Plan WWhat information is given? 99 volts, 3 bulbs x 0.5 ohms = 1.5 ohms plus 3 ohms for total of 4.5 ohms. What formula do I use? II = v / r II = 9 v / 4.5 Ω Solve II = 2 amps Check:Does it make sense? TThe current is less than the voltage because the resistance is reducing the flow

Circuits and Current Direction

Series Circuit  Only one path for electricity to flow What happens if one bulb goes out? Will the bulbs be dimmer or brighter than a parallel? Load (bulb) Switch

Parallel circuit  More than one path for electricity to flow Each load on separate circuit What happens if one bulb goes out?  Compare series/parallel to water supply

Current Direction CCurrent always flows in one direction: From negative to positive AC vs. DC

Direct Current DC  Charges always flow in same direction, from negative terminal to positive terminal Battery (cells)

Cells and Batteries CConvert chemical energy to electrical energy Potato clock Electron acceptor Electron donor anode collector plastic seal anode plastic sleeve steel jacket Case sleeve Cell straps Negative terminal Positive terminalelectrolyte cathode collector cathode 9 Volt Battery

Other sources of DC  Thermocouple: convert heat to electricity  Solar cells: convert solar energy to electricity

Alternating Current AC  Charges flow from negative to positive but switch directions back and forth (alternate) House current

Producing AC current IInduction: Coil of wire and magnet produce electricity IIt’s electro-magnetism! Generator: converts mechanical energy to electrical energy Motor: converts electrical energy to mechanical energy

Electromagnetism  Magnetism and Electricity are closely related  Electric current causes magnetic fields Cell phones, television, light  Magnets can cause an electric current to flow Generators

Power  Measures how fast energy is transferred from one form to another  Measured in Watts Power = voltage x current  P= V I  A 100 watt light bulb changes or uses electrical energy to light energy twice as fast as a 50 watt bulb  Brainpop on current Brainpop on current