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.