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Introduction to Electricity
Static Electricity and Electrical charge
Atoms and charge
Atoms are made of protons, neutrons and Electrons.
Protons- positiveNeutrons- neutralElectrons- negative
Charges of particles
Law of Electrical charges
Like charges repel and opposite charges attract.
The force betweencharged objects is Electrical force.
Electrical force
Strength of electrical force determined by•Size of the charge -greater charge = more force•Distance from charge- close=greater
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!!
Charge by friction
Rubbing 2 objects together to separatePositive and negative charges.
Charging by conduction
When electrons are transferred from one Object to another by direct contact
Charge by inductionOccurs when charges in uncharged objectAre rearranged without direct contactWith charged object
Conservation of charge
Charges are not created nor destroyed,Just moved from atom to atom
Detecting charge
Electroscope can detect if an object is charged
Moving electrical charges
Materials are divided into 2 groups basedOn how easily a charge can travel through it
Conductors or Insulators
Conductors
Allow charges to move easily through them•Electrons in metals are free to move about•Used to make wires •Not always metals (water)
InsulatorsMaterials that do not allow easy charge movement•Electrons are tightly bound•Used to coat conductors to prevent shock
Static electricity
Build-up of electrical charge•Charges are not moving•Created by opposite charges
Lightning
Occurs when charge is separated in cloudAnd induces opposite charge on the surface
Section 2Electrical energy
Batteries uses chemical reactions to Produce electrical energy.
Batteries
Cells- device that produces an electricalcurrent by converting chemical energy toelectrical energy.
Battery- uses several cells to make energy
Parts of a cell
Batteries contain electrolytes (a mixture ofchemicals)
Chemical reaction in electrolytes convert chemical energy to electrical energy
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.
Types of cells
Dry cells- use solid or paste-like electrolyte
Wet cells- use sulfuric acid as electrolyte
Potential differenceEnergy per unit charge expressed in volts
Chemical reaction causes difference incharge between electrodes.
More cells = more potential difference
Other ways to produce electrical energy
Photocells- solar panel converting light to Electrical energy
Thermocouple- thermal energy convertedTo electrical energy
Section 3 Electric Current
Current- rate at which charge flows
Ampire (AMP)- unit for current
Voltage- difference between energyper unit charge
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
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
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
Ohms LawShows voltage, current and resistanceAre related with the following equation
V = I x R R = V / II = V / R
V = voltageR= ResistanceI= Current
Electrical Power
The rate at which electrical energy is usedTo do work.
Power (W) = voltage (V) X current (Amps)
Power rating
Measured in watts for light bulbs and all Electrical appliances and devices
Kilowatt-hours for measuring householdElectricity use.
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