10.2: Electricity and Electric Circuits

Static vs. Current Electricity• Static Electricity:

charges build up in one location

• Current Electricity: electrons on the move

Current Electricity

• to operate electrical devices, you need a steady flow of electrons.

• Current electricity is the continuous flow of electrons in a circuit.

• The electrons flow continuously if the following conditions are met:

1. there is a continual supply of energy2. the electrons have a a complete path to flow through

(electric circuit)

Electric CircuitsAn electric circuit must include:

1. An energy source – “energizes” the electrons, ex. battery, photoelectric cell in calculator

2. a conducting wire (connector) – provides a path for current to flow

3. A load which is a device that converts electrical energy to another form of energy, ex. light bulb

Many electric circuits also include a switch that turns the circuit on or off by closing or opening the circuit.

Examples of Loads

Examples of Loads

Converts electricity to…

light bulb light energy

fan mechanical energy

doorbell sound energy

Schematic Circuit DiagramsSchematic Circuit Diagrams

• engineers and designers of electrical circuits use special symbols that show the components and connections in a circuit.

• a drawing made with these symbols is called a circuit diagram.

Schematic Circuit DiagramsSchematic Circuit Diagrams

• Follow these rules when you draw circuit diagrams.

1. Always use a ruler to draw straight lines for the conducting wires.

2. Make right-angle corners so that your finished diagram is a rectangle.

Circuit SymbolsCircuit Symbols

• Conductor or wire– allows current to flow very easily from one part

of a circuit to another.

Circuit SymbolsCircuit Symbols

• Cell - supplies electrical energy-the positive end is bigger than the negative end.

Circuit SymbolsCircuit Symbols

• 2 Cells

• Note: every time a cell is added you need to draw another cell; a battery is a combination of two or more cells

Circuit SymbolsCircuit Symbols

• Ground

– a connection to earth

Circuit SymbolsCircuit Symbols• Switch - an on-off switch allows current to flow

only when it is in the closed (on) position

Circuit SymbolsCircuit Symbols

• Lamp

– a load which converts electrical energy to light

Circuit SymbolsCircuit Symbols

• Resistor

– A resistor restricts the flow of current

Circuit SymbolsCircuit Symbols

• Ammeter – device that measures current

A

Circuit SymbolsCircuit Symbols

• Voltmeter

• device that measures voltage

V

Circuit SymbolsCircuit Symbols

Motor -electrical load that converts electrical energy into movement

M

Circuit BuildingCircuit Building

• Draw the circuit diagrams for each circuit described on the handout

– Now try building the circuit (substitute the buzzers for the motors)