Electricity and Magnetism

electric field

a region around a body where an electric force is experienced

direction of an electric field

the direction of the force on a small positive charge placed at that point in the field

hazards of static electricity

electric shock from lightning, explosions when refueling vehicles/aircrafts

useful applications of static electricity

dust extraction in chimneys, painting new vehicles, application of pesticides, photocopying machines

conductor

allows an electric current to flow through it examples copper, aluminum, mercury, water, sodium chloride solution

non-conductor/insulator

does not allow an electric current to flow through it examples plastic and rubber

semi-conductor

allows current to flow through it under certain conditions example silicon

charge carriers in metals

electrons

charge carriers in electrolytes

cations and anions

charge carriers in semi-conductors

‘holes’ and electrons

types of semi-conductors

n-type and p-type materials

n-type material

semi-conductor where electrons are the majority charge carriers eg silicon doped in phosphorus

p-type material

semi-conductor where holes are the majority charge carriers eg silicon doped in boron

electric current

the rate of flow of charge

1 coulomb

the charge flowing through a point in a circuit when a current of 1 Ampere flows for a duration of 1 second

flow of conventional current

positive to negative

flow of electrons

positive to negative

electrons vs current

electrons are the particles which flow to create current whereas current is the rate of flow of the electrons

direct current

flows in one direction only

alternating current

the current flow reverses direction regularly with time

potential difference

the energy converted from electrical to other forms per unit Coulomb of charge flowing

electromotive force

the energy converted from other forms to electrical per unit Coulomb of charge flowing

pd vs emf

emf is the energy supplied by a power source to push electrons through a circuit which causes the current to flow whereas pd is the energy used up by the current in different parts of the circuit so emf creates the current while pd is the energy used up by the current in different parts of the circuit

how are pd and emf measured

using a voltmeter

energy transformation in a light bulb

electrical to light and heat

energy transformation in a loudspeaker

electrical to sound

energy transformation in an electric motor

electrical to kinetic and heat and sound

energy transformation in a solar panel

light to electrical

energy transformation in a turbine

kinetic to electrical

electrical energy production in turbines

natural gas is used to boil water to produce steam, the steam turns the turbines and electricity is produced

renewable energy sources

wind, geothermal, solar, biomass, tidal

non-renewable energy sources

natural gas, coal, oil

how to conserve electrical energy

switch out incandescent light bulbs with fluorescent bulbs, use LED bulbs instead, unplug devices not in use, hang clothes instead of using a dryer

Primary cell (dry cell)

Chemical reactions inside the dry cell produces electricity when the reactions stop the battery can no longer be used

Secondary cell

Chemical reactions produce electricity and the battery can be repeatedly recharged