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# Electricity - PowerPoint PPT Presentation

Electricity. The flow of charges. Atoms. 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:

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## PowerPoint Slideshow about ' Electricity' - belle

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Presentation Transcript

### Electricity

The flow of charges

• Nucleus: Protons and neutrons

• Electrons: negative charge orbit nucleus

• Flow of electrons

• Measured in Amperes (Amps)

• Electrons passing per second

• Must have complete, unbroken path for current to flow

• 3 Parts:

• Load: device run by electricity

• Wires: path for electron flow

• Source: moves the electrons through the wire

• Battery, generator, wall socket (power plant)

• Materials allowing electrons to flow

• Examples:

• metals: electrons loosely held, move easily

• Copper is one of the best

• Do not allow electricity to flow

• Examples: rubber, plastic

• Electrons held tightly, will not move easily

• Measures the force “pushing” electrons

• Volt (v) as unit

• Higher voltage is higher potential to push electrons through circuit

Lower Potential energy =Low voltage

Higher Potential energy=high voltage

• Force working against (“resisting”) the flow of electrons

• Measured in Ohms (Ω)

• All parts of circuit “slows the flow”

I =

R

Ohm’s Law

• Tells how current, voltage, resistance are related

• Current = voltage

resistance

• 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

• What information is given?

• 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 = v / r

• I = 9 v / 4.5 Ω

• Solve

• I = 2 amps

• Check:Does it make sense?

• The current is less than the voltage because the resistance is reducing the flow

### Circuits and Current Direction

• Only one path for electricity to flow

• What happens if one bulb goes out?

• Will the bulbs be dimmer or brighter than a parallel?

Switch

• 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 always flows in one direction:

From negative to positive

AC vs. DC

• Charges always flow in same direction, from negative terminal to positive terminal

• Battery (cells)

plastic seal

plastic sleeve

anode

steel jacket

Case sleeve

Cell straps

cathode

Negative terminal

cathode collector

electrolyte

Positive terminal

Cells and Batteries

9 Volt Battery

• Convert chemical energy to electrical energy

• Potato clock

Electron acceptor

Electron donor

• Thermocouple: convert heat to electricity

• Solar cells: convert solar energy to electricity

• Charges flow from negative to positive but switch directions back and forth (alternate)

• House current

• Induction: Coil of wire and magnet produce electricity

• It’s electro-magnetism!

• Generator: converts mechanical energy to electrical energy

• Motor: converts electrical energy to mechanical energy

• Magnetism and Electricity are closely related

• Electric current causes magnetic fields

• Cell phones, television, light

• Magnets can cause an electric current to flow

• Generators

• 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