Electric Circuits

• Georg Ohm found that conductors and most other devices have a constant resistance regardless of the applied voltage

• Ohm's law says that resistance in a circuit is equal to voltage divided by current

• Resistance = V = I × R

• Units for resistance (Ohms); voltage (volts - V), Current is amps (A)

• Objects that use electricity contain circuits

• All electric circuits have these basic features: devices that run on electrical energy, sources of electrical energy, and conducting wires

• Power plants and batteries are examples of energy sources

• These supply the voltage that causes current to flow

• When the energy source is a battery, current flows from the positive end to the negative end

• Energy is always conserved in a circuit (meaning energy does not get used up)

• Instead, energy is transformed into other forms of energy (ex. heat, light, mechanical, and sound energy)

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• Electric circuits are connected by conducting wires. These wires complete the path of the current.

• Wires allow charges to flow from the energy source to the device that runs on electric current...and then back to the energy source

• Often a switch is used to control the current. Opening a switch breaks the circuit, which shuts off the device

-Drawings of circuits have symbols to represent the parts

-See the image to the right to see the parts labeled

• A series circuit has only one path for the current to take

• If one light goes out, the other lights go out as well

• Light bulbs in the circuit will become dimmer as more bulbs are added. This is because the resistance increases.

• Many paths for current to take

• Because there are multiple pathways currents can take, if one bulb goes out, the others remain lit

• Resistance actually decreases by adding extra pathways because you increase pathways for electric current to follow

• So, adding pathways will not change bulb brightness