Introduction to Electricity Static Electricity and Electrical charge

Atoms and charge Atoms are made of protons, neutrons and Electrons. Protons- positive Neutrons- neutral Electrons- negative Charges of particles

Law of Electrical charges Like charges repel and opposite charges attract. The force between charged 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 because Atoms can either gain or lose electrons Gain electrons = negative charge Lose electrons= positive charge Atoms can’t lose protons or neutrons!!

Charge by friction Rubbing 2 objects together to separate Positive and negative charges.

Charging by conduction When electrons are transferred from one Object to another by direct contact

Charge by induction Occurs when charges in uncharged object Are rearranged without direct contact With 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 based On 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)

Insulators Materials 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 cloud And induces opposite charge on the surface

Section 2 Electrical energy Batteries uses chemical reactions to Produce electrical energy.

Batteries Cells- device that produces an electrical current by converting chemical energy to electrical energy. Battery- uses several cells to make energy

Parts of a cell Batteries contain electrolytes (a mixture of chemicals) Chemical reaction in electrolytes convert chemical energy to electrical energy

Simple cell Pair of electrodes made from 2 different conducting 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 difference Energy per unit charge expressed in volts Chemical reaction causes difference in charge between electrodes. More cells = more potential difference

Other ways to produce electrical energy Photocells- solar panel converting light to Electrical energy Thermocouple- thermal energy converted To electrical energy

Section 3 Electric Current Current- rate at which charge flows Ampire (AMP)- unit for current Voltage- difference between energy per unit charge

AC/DC AC or Alternating current- current can flow any 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 electrons Think 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 increase resistance Temperature- higher temps = higher resistance

Ohms Law Shows voltage, current and resistance Are related with the following equation V = I x R R = V / I I = V / R V = voltage R= Resistance I= Current

Electrical Power The rate at which electrical energy is used To 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 household Electricity use.