ELECTRIC CIRCUITS

ELECTRIC CIRCUITS

Electric Circuits

What is an electric circuit?

SO EASY! A circuit is a loop of wire with its ends connected to an energy source such as a cell or a battery.

Circuit Basics

One end of the wire is connected to the positive terminal; the other end of the wire is connected to the negative terminal. The wire is connected in this way so a current can flow through it.

Series Circuits Parallel Circuits

The defining property of series circuits is that all their components (lamps, cells, switches, etc.) are connected in one loop of wire

Because it has only one circuit, a series circuit has just one current

A parallel circuit is like two or more series circuits connected to the same energy source

The components lie inside "parallel" loops connected to the same energy source.

Simple Circuit Parallel Circuit

There advantage to having a parallel circuit over a simple circuit is that a failure of one component of a parallel circuit does not lead to the failure of the other components because a parallel circuit consists of more than one loop and has to fail in more than one place before the other components fail

Circuit Symbols

ammeter

           cell

    fuse

               battery of two cells

     

diode

           lamp

           lamp (old)

           switch (open)            

switch (closed)            

voltmeter

           variable resistor

              

thermistor

              

Ωhm’s ζαψςOhm’s Law expresses the relationship

between voltage, resistance and current is expressed in Ohm's Law :

V = IR (Voltage = Current × Resistance )

Current is directly proportional to voltage for a metal conductor at a constant temperature, so if the voltage goes up, so will the current

Resistance & Resistors

Although we may not usually notice it, we are always subject to resistance

To understand resistance, try to imagine the difference between walking normally and walking in a pool

It's the same for a current moving through a conductor

ConductorsAll conductors offer resistance to the flow of current. This resistance is determined by the conductor's atoms

In conductors, atoms offer negligible resistance to an electric current because a significant proportion of their electrons are free to move from atom to atom.

Silver and Copper are examples of good conductors

Insulators

The atoms of insulators offer very considerable resistance to an electric current because a significant proportion of their electrons are not free to move from atom to atom

A conductor's length, temperature, and cross-sectional area also affects its resistance

Glass and synthetic polymers are examples of good insulators

THE END!

By Alex Chang and Dan Stathatos