Chapter 5

Sources of Electricity

Chemical Action

Alessandro Volta Invented the electric cell – voltaic cell The term volt Discovered that electrical potential

was created when dissimilar elements were placed in a chemical.

Chemical ActionDissimilar metals placed in an acid and water solution (electrolyte)This action produces a surplus of electrons and when a load is placed a current will flow. Chemicals are used up therefore cannot be recharged.Primary cell – a cell in which the chemical action cannot be reversed (recharged)

Types of Primary Cells

Dry cells – electrolyte is a paste Zinc-carbon cell Alkaline cell Mercury cell – 5 times more current

than conventional dry cells. Lithium cell Silver oxide cell

Secondary Cell

Can be recharged or restored Car Battery Rechargeable Batteries

Nickel-Cadmium cell Lithium-Ion

Specific Gravity – weight of a liquid as it is compared to water. (electrolyte in a battery)

Hydrometer – used to measure specific gravity.

Lead Acid Cell

Combinations of Batteries

Series

Voltage accrues Eout = E1+E2+E3+E… Eout = 1.5v + 1.5v +1.5v +1.5v = 6v

Amperage does not increase Iout = I1=I2=I3=I… Iout = 1A

ParallelVoltage is the same as one cell only

Eout = E1=E2=E…

Eout = 1.5v

Amperage accruesIout = I1+I2+I3+I…

Iout = 1A+1A+1A+1A

=4A

Series - Parallel

Treat each area of the circuit separately, then combine them.

Treat these rows as Series

Treat whole thing as Parallel

Other Sources

Photovoltaic – solar cell / photocell Made from crystalline silicon mixed

with impurities to form a positive and negative semi-conductor material.

When exposed to light an electrical potential is developed.

Cells – Modules – Panels – Array

Photovoltaic Cell

N-type semiconductorP-type semiconductor

Other Light sensitive Components

Photoresistive cell – light sensitive resistors (varies current based on amount of light)

Electricity from Heat

Thermocouple – a device used to indicate and control the heat of electronic devices.When two dissimilar metals in contact with one another and are heated, a potential difference is developed.Galvanometer – used to measure very small currentsPyrometer – meter/thermocouple combinationThermopile – group of thermocouples

Electricity from Mechanical Pressure

Crystal properties Distortion when voltage applied Voltage when pressure is applied Piezoelectric effect – creating

electricity by the mechanical distortion of a crystal. Crystal microphones

Fuel Cell

Potential difference created by hydrogen gas and oxygen gas combining with potassium hydroxide. Theoretically 100% efficient Little pollution

Magnetohydrodynamic Power

Electricity that is generated when an ionize gas is passed through a magnetic field. Cathode – negative plate Anode – positive plate

Generator

The production of electricity by the use of magnetism in a mechanically rotating machine.Dynamo