# Electric Circuits Electric charges always move from high-voltage to low-voltage. Travels from negative to positive [http://www.energyquest.ca.gov/story/images/chap04_circuit.gif]

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Electric Circuits Electric charges always move from high-voltage to low-voltage. Travels from negative to positive [http://www.energyquest.ca.gov/story/images/chap04_circuit.gif] Click Here for an Interactive Example

Electric Circuits Voltage difference “forces” charges along a conductor and is measured in volts (V) Also called potential difference [http://www.speedysigns.com/images/osha/large/DANGER54.gif]

[http://www.bcae1.com/images/gifs/voltage1.gif] Water Tower analogy for Voltage

Electric Circuits Electric Current is the flow of charges (electrons) and is measured in amperes (A). [http://www.heirloomradio.com/images/coulomb.jpg]

[http://www.smud.org/safety/world/hurt/media/current_chart.gif]

Electric Circuits Resistance is the tendency for materials to oppose the flow of electrons. Electrical energy is commonly changed into heat, light, or motion. [http://www.energyquest.ca.gov/story/images/chap04_circuit.gif]

Electric Circuits Resistance is measured in ohms (Ω). Click here for a video example of resistance. phttp://www.cartoonstock.com/newscartoons/cartoonists/ksm/lowres/ksmn1044l.jpg]

Ohm’s Law As the resistance in the circuit increases, the current (number of charges) decreases. V = I R Click Here for an Interactive Example

Ohm’s Law Example: A circuit has a resistance of 0.5 Ω and has a current of 3.0 A. What size battery in volts is needed? V = (3.0 A) x (0.5 Ω) V = 1.5 V

Ohm’s Law Example: A 9-volt battery is used in a circuit with a resistance of 1.5 Ω. What current is needed? (9 V) = I (1.5 Ω) (1.5 Ω) I = 6.0 A

Circuit Diagrams A 2-dimensional representation of an electrical circuit. [http://www.ise5-14.org.uk/Prim3/New_Guidelines/Newsletters/9/IMGS/bulb.gif]

Some diagram symbols include… Open Switch Light Bulb Voltmeter Ammeter or

Series Circuits The current only has one possible circuit to pass through. [http://iss.cet.edu/electricity/pages/images/B/b13_2.jpg]

[http://www.danieltrimpey.com/learn/electronics/images/series.GIF] 1 2 3

Parallel Circuits There are two or more branches on each circuit for current to move through. [http://iss.cet.edu/electricity/pages/images/B/b13_3.jpg]

123 [http://www.danieltrimpey.com/learn/electronics/images/series.GIF]

Circuit Protection Devices If too much current flows through a circuit, a safety device shuts off the current in order to prevent it from overheating.

Circuit Protection Devices Fuses A small piece of metal that will melt if too much current passes through it. [http://hollyfuse.en.alibaba.com/product/50020315/50104654/5_phi__Fuses/50T_Fuses/showimg.html]

May only be used once, then must be replaced.

Circuit Protection Devices Circuit Breaker A piece of metal bends if too much current passes through, and it turns off the switch to the circuit. Just need to reset the switch to use again [http://www3.sympatico.ca/mmatkiwsky/reng/images/Trailer/breakers.JPG]

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