Electricity

• whether two charges attract or repel depends on whether they have the same or opposite sign

• unit of measurement for charge is the coulomb (C)– one electron has a charge of

0.00000000000000000016 coulombs

Charge

Current

• comes from the motion of electrons• is the rate at which electrons flow past a point

on a circuit– measured in units called amperes, or amps (A)

current

Voltage• a measure of electric potential energy• voltage is an electrical force

– measured in volts (V)• a difference in voltage provides the energy that

causes current to flow

Circuits• current only flows when there is a complete

and unbroken path, or a closed circuit

• A circuit with a break is an open circuit and will trop the current. Example: light switch

• Electricity and Circuits (8:35)– http://www.youtube.com/watch?v=D2monVkC

kX4&feature=related

• series circuit– current can only take one path, so the

current is the same at all points in the circuit

• parallel circuit– the current can take more than one path– each branch works independently

• Resistance– The measure of how strongly a wire or other

object resists current flowing through it– The amount of resistance determines the

amount of current for a given voltage. Higher resistance = less current.

Full Current ½ current 1/3 current

Conductors, Semiconductors and Insulators– Conductors: can conduct, or carry, electrical current.

The resistance is low. Example: metals

– Insulator: current cannot pass easily through these materials because the insulate, or block, the flow of the electrical current. Examples: rubber, glass, wood

– Semiconductor – between a conductor and insulator. They carry electricity better than an insulator but not as good as a conductor. Examples include: silicon (used in computer chips, TV, portable radios)

Insulator