Electric Circuits 20.3

Circuit Diagrams An electric circuit is a complete path through which charge can flow. Circuit diagrams use symbols to represent parts of a circuit, including a source of electrical energy and devices that are run by the electrical energy.

Simple Circuit

Simple Circuit

Circuit Diagrams A circuit diagram shows one or more complete paths in which charge can flow. Switches show places where the circuit can be opened. If a switch is open, the circuit is not a complete loop, and current stops (open circuit).

Open Circuit

Series Circuits In a series circuit, charge has only one path through which it can flow. If one light bulb burns out in a series circuit, it becomes an open circuit and none of the elements can operate. EX: Christmas tree lights

Series Circuit

Series Circuit

Series Circuit The bulbs in a circuit are a source of resistance. Adding bulbs to a series circuit increases the resistance. As a result the current decreases and each bulb shines less brightly.

Parallel Circuits A parallel circuit is an electric circuit with two or more paths through which charges can flow. If one bulb burns out, charge still flows along the other path, and the other bulb stays lit. Each circuit is wired in parallel so they can operate independently.

Parallel Circuit

Parallel Circuit

Ohm’s Law Voltage = Current x Resistance V = I x R

Power and Energy Calculations Power is the rate of doing work. The rate at which electrical energy is converted to another form of energy is electric power. The SI unit of electric power is watt (W)

Power and Energy Calculations Electric power can be calculated by multiplying voltage by current. P (watts) = I (amps) x V (volts) Electrical Energy (E) = P x t

Electrical Safety Correct wiring, fuses, circuit breakers, insulation, and grounded plugs help make electrical energy safe to use.

Home Safety A fuse prevents current overload in a circuit. If too much current passes through a fuse the fuse will melt (blowing a fuse). A circuit breaker is a switch that opens when current in a circuit is too high. The transfer of excess charge through a conductor to Earth is called grounding.

Fuse and Circuit Breaker

Electronic Devices 20.4

Electronic Signals An electronic signal is information sent as patterns in the controlled flow of electrons through a circuit. Electronics conveys information with electrical patterns called analog and digital signals.

Vacuum Tubes Vacuum tubes can change alternating current into direct current, increases the strength of a signal, or turn a current on or off.

Semiconductors A semiconductor is a crystalline solid that conducts current only under certain conditions.

Solid-State Components Most modern electronic devices are controlled by solid state components. Three of the most useful solid state components are diodes, transistors, and integrated circuits.

Diodes, Transistors, Integrated Chips A diode can change alternating current to direct current. A transistor is three semiconductors that can be used as a switch to turn current on or off. Integrated circuits are microchips that contains many solid state components.