Electricity

Sections 2 and 3

Electric Energy

Cells/Batteries

- Cell - device that produces an electrical current by converting chemical energy into electrical energy

- Battery – is made of several cells

Parts of a Cell•Electrolyte – mixture of chemicals that

conduct a current•Chemical reactions in the electrolyte convert chemical

energy into electrical energy

–

•Electrodes – part of the cell through which charges enter or exit

•Two different electrodes made of different conducting material

Electrolyte

ElectrodeElectrode

Potential Difference• The current between the two electrodes

exists because of the chemical reaction in the electrolyte causing the electrodes to become charged differently

• This electric current that is produced causes energy. The energy is the POTENTIAL DIFFERENCE (Volts,V)

Potential Difference• The greater the potential difference, the

greater the current.

Electric Current• The RATE at which charges flow through a

material.❖Unit is Ampere (A)

➢ The number of amps describes the amount of charge flowing past a given point.

❖ Symbol in an equation is I

page 167- Fig. 1

Voltage•Another word for potential difference

– difference in energy per unit charge as it moves between two points in the path of a current

•Expressed in Volts (V)

•Symbol in an equation is V

Resistance•Opposition to the flow of electric charge–Holds the charge back from flowing

–

–Expressed in Ohms ( Ω )

–Symbol in an equation is R

–

–The more resistance – the less flow/lower the current

Resistance•

The amount of resistance depends on material, thickness, length, and

temperature

If more than one path for current is available, the current will flow through the

path that has the least resistance.

Tying it all togetherOhm’s LawI = V/R

Current = Voltage

Resistance

Amphers (A) = Volts (V)

ohms (Ω)

CircuitsCircuit = complete, closed path through which electric

charges flow

PARTS

–load: device that uses electrical energy to do work– Light bulbs, appliances, motors

»Causes electrical energy to change into a different type of energy such as light or kinetic energy

–Wires

–Energy sourceA switch is sometimes used

Types of Circuits - Series•Circuit where all parts are connected in a

single loop

•Follow one path

•All of the loads share the same current

•

•The more loads you add, the more resistance is created, therefore, lowering the amount of current

Series CircuitUses:

- Automatic door at the grocery store

Parallel Circuits

•Circuit in which different loads are located on separate branches

•Charges can follow more than one path

•Loads do not have/share the same current

–Each load uses the same as what the voltage is

•If one of the loads goes out, the rest will still work unlike a series circuit because the current will find a different branch to travel

Circuit Diagram Symbols