introduction to electricity static electricity and electrical charge
TRANSCRIPT
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Introduction to Electricity
Static Electricity and Electrical charge
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Atoms and charge
Atoms are made of protons, neutrons and Electrons.
Protons- positiveNeutrons- neutralElectrons- negative
Charges of particles
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Law of Electrical charges
Like charges repel and opposite charges attract.
The force betweencharged objects is Electrical force.
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Electrical force
Strength of electrical force determined by•Size of the charge -greater charge = more force•Distance from charge- close=greater
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Charging atoms
Objects can become charged becauseAtoms can either gain or lose electrons
Gain electrons = negative chargeLose electrons= positive charge
Atoms can’t lose protons or neutrons!!
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Charge by friction
Rubbing 2 objects together to separatePositive and negative charges.
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Charging by conduction
When electrons are transferred from one Object to another by direct contact
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Charge by inductionOccurs when charges in uncharged objectAre rearranged without direct contactWith charged object
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Conservation of charge
Charges are not created nor destroyed,Just moved from atom to atom
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Detecting charge
Electroscope can detect if an object is charged
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Moving electrical charges
Materials are divided into 2 groups basedOn how easily a charge can travel through it
Conductors or Insulators
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Conductors
Allow charges to move easily through them•Electrons in metals are free to move about•Used to make wires •Not always metals (water)
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InsulatorsMaterials that do not allow easy charge movement•Electrons are tightly bound•Used to coat conductors to prevent shock
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Static electricity
Build-up of electrical charge•Charges are not moving•Created by opposite charges
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Lightning
Occurs when charge is separated in cloudAnd induces opposite charge on the surface
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Section 2Electrical energy
Batteries uses chemical reactions to Produce electrical energy.
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Batteries
Cells- device that produces an electricalcurrent by converting chemical energy toelectrical energy.
Battery- uses several cells to make energy
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Parts of a cell
Batteries contain electrolytes (a mixture ofchemicals)
Chemical reaction in electrolytes convert chemical energy to electrical energy
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Simple cell
Pair of electrodes made from 2 differentconducting metals are In contact with electrolyte.
Electrode- part of a cell through which charges enter and exit.
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Types of cells
Dry cells- use solid or paste-like electrolyte
Wet cells- use sulfuric acid as electrolyte
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Potential differenceEnergy per unit charge expressed in volts
Chemical reaction causes difference incharge between electrodes.
More cells = more potential difference
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Other ways to produce electrical energy
Photocells- solar panel converting light to Electrical energy
Thermocouple- thermal energy convertedTo electrical energy
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Section 3 Electric Current
Current- rate at which charge flows
Ampire (AMP)- unit for current
Voltage- difference between energyper unit charge
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AC/DC
AC or Alternating current- current can flowany direction in a wire• home wiring
DC or Direct current- current only flows in one direction.•Batteries, flashlights
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Voltage and resistance
US households supply a voltage of 120 V
Resistance – opposition of flow of electronsThink of this as electrical friction.
Resistance is expressed in OHM’s
As resistance increases, current decreases
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Factors that affect resistance
•Conductor type- copper good, iron bad•Thickness of wire – thicker wires decrease resistance•Length of wire- longer wires increaseresistance•Temperature- higher temps = higher resistance
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Ohms LawShows voltage, current and resistanceAre related with the following equation
V = I x R R = V / II = V / R
V = voltageR= ResistanceI= Current
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Electrical Power
The rate at which electrical energy is usedTo do work.
Power (W) = voltage (V) X current (Amps)
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Power rating
Measured in watts for light bulbs and all Electrical appliances and devices
Kilowatt-hours for measuring householdElectricity use.