Chapter 19: Chapter 19: Electric Charges and CurrentsElectric Charges and Currents

19-4 and 19-5: 19-4 and 19-5: Electric Circuits and Electric Electric Circuits and Electric

PowerPower

Electric CircuitsElectric Circuits

• An electric circuit provides a complete, closed path for an electric current.

• An electric circuit consists of a source of energy (voltage source), a load (resistance), wires, and a switch

Electric CircuitsElectric Circuits

• SourceSource:: battery, thermocouple, etc.

• LoadLoad:: uses electric energy (light bulb, appliance, etc.) - offers some resistance to current flow

• SwitchSwitch:: opens and closes the circuit

• A current needs a closed path - if a switch A current needs a closed path - if a switch is off, the circuit is open.is off, the circuit is open.

Parts of an Electric CircuitParts of an Electric Circuit

Load (Light Bulb)

Source (Battery)

Electric CircuitsElectric Circuits

• Electricity cannot flow through an open circuit. Electricity can only flow through a closed circuit.

Closed CircuitClosed Circuit Open CircuitOpen Circuit

Series and Parallel CircuitsSeries and Parallel Circuits

• SeriesSeries CircuitCircuit:: circuit in which all parts are connected one after another. If there is a break, the entire circuit is opened and no current flows

• ParallelParallel CircuitCircuit:: circuit in which different parts are on separate branches. If there is a break, electrons can still move.

Series and Parallel CircuitsSeries and Parallel Circuits

Series CircuitSeries Circuit

Parallel CircuitParallel Circuit

Series and Parallel CircuitsSeries and Parallel Circuits• FuseFuse:: this strip of metal

used for safety because when the current flowing through it becomes too high, it melts and breaks the flow of electricity

- Protects against too much current flow (overload)

- Once fuses burn out they must be replaced

Series and Parallel CircuitsSeries and Parallel Circuits

• Circuit Breaker: reusable device that protects a circuit from being overloaded

- Easier to use than fuses

Electric PowerElectric Power

• Electric Power is the ratio at which electric energy is used by doing work, or by changing to a different form, such as heat or light

Power = Voltage x Current

P = V x P = V x II

Watts = Volts x Amperes

Electric EnergyElectric Energy

Energy = Power x Time

E = P x tE = P x t

Kilowatt-hours = Kilowatts x hours