Circuits in your home

The difference in electrical potential energy between 2 places in an electrical field

(potential difference=voltage)

**charges flow from greater PE to lower PE

units= Volts (V)

Opposition to the flow of charge

Resistance depends on:

• thickness: thicker wire= less resistance
• (e- can pass through easier)
• length: longer=more resistance
• (charges have to travel further)
• temperature: higher temp= greater resistance
• (higher temp= e- colide more frequently)

units= ohm

Symbol= R or

• rate at which charges move through a conductor

(flow of e- through a wire)

• current actually flows in the opposite direction from the flow of charges because scientists define current as the direction in which positive charges flow

Units= ampere/ amps (A)

symbol= I

Additional Resources

Article on Direct current: http://www.physics4kids.com/files/elec_dc.html

Article on Alternating current: http://www.physics4kids.com/files/elec_ac.html

AC vs DC article and video http://kids.britannica.com/lm/animations/oaltern001d4/product.html

Article on Ohm's Law: http://www.ducksters.com/science/physics/ohms_law.php

Electrical Energy

power companies charge based on the amount of electrical energy used rather than electrical power

Unit= kilowatt- hours (kWh)

EE= electrical power (kW) x time (hours)

Cicuits in your House

There are two types of current

Voltage:

What is a Circuit breaker?

Alternating

Direct

Resistance

Alternating Current

Direct current

• You have PARALLEL circuits in your home
• If you have many small appliances drawing current from the same circuit, more current will flow
• As current increases so does heat
• Heat can melt wire and thus start fires
• To protect against this, you have fuses and circuit breakers.

Heating elements Use more energy than other appliances

Ohm's Law

• A.C. regularly reverses it's direction
• (ex: electricity in homes)

• A circuit breaker contains a piece of metal that bends when the current gets high and heats it up. .
• When the metal bends it flips the the switch and shuts off the circuit.

(you can turn it back "on" but, first shut off some appliances)

• D.C. Flows in only one direction
• (ex: battery opperated devices)

• i.e: ovens, hair dryers
• Hair dryer= 1875 W
• Microwave= 1600W

Current

As electrons move through a conducting wire the collide with other electrons and ions. these collisions convert some of the KE in the moving charges to thermal energy. Therefore there is less energy available to move the electrons, thus the current is reduced)

• states that the current passing through a conductor is proportional to the voltage over the resistance.
• increase voltage=increase in current
• same voltage+ increase in resistance= decrese current

Faraday's Law:

a change the magnetic fields will induce (created) current and voltage

What is a fuse?

A fuse is: a safety device consisting of a strip of wire that melts and breaks an electric circuit if the current exceeds a safe level.

Electrical Power

rate at which electrical energy is converted to another form of energy

Ex: fan= electrical to mechanical

light bulb= electrical to light and heat

Unit= Watts (W) or kilowatts (kW)

1kW=1000W

Current x Voltage= Power (P=IV)

Circuits in your home

and Ohm's LAW