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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: - PowerPoint PPT Presentation
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Electricity
The flow of charges
AtomsMade up of:
Nucleus: Protons and neutrons
Electrons: negative charge orbit nucleus
CurrentFlow 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 electricity2. Wires: path for electron flow3. 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
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 relatedCurrent = voltage
resistance
I = VR
Practice Ohm’s Law
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
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 Current always flows in one direction:From negative to positive
AC vs. DC
Direct CurrentDC
Charges always flow in same direction, from negative terminal to positive terminal Battery (cells)
Cells and Batteries Convert chemical
energy to electrical energy Potato clock
Electron acceptor
Electron donor
anode collector
plastic sealanode
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 CurrentAC
Charges flow from negative to positive but switch directions back and forth (alternate) House current
Producing AC 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
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