CHAPTER 2

Open Circuits Closed Circuits  Open Switch = device is off  Stops the circuit  Closed switch = device is on  Batteries have connections at both ends so charge can follow a closed path

CircuitShort Circuit  Follows the path of the least resistance  Intended path  Useful path  Controls current  Follows the path of the least resistance  Unintended path  Accidental damage to wire  Dangerous

 Fuses: ◦ Consists of a metal strip that is inserted into the circuit ◦ A safety device that opens a circuit when there is too much current in it (metal strip melts)  “Fuse is blown” ◦ Will automatically shut off the current ◦ Usually in older homes and buildings  Circuit Breakers: ◦ Automatically open the circuit when too much charge flows through it ◦ Do not have to be replaced every time they open the circuit (unlike fuses) ◦ Wire inside will grow hot and expand  flips the switch off ◦ Once problem is solved, switch can be manually flipped to on again

Chapter 2.3

 A code is a system of symbols used to send a message ◦ Language  Electronic device – uses electric current to represent coded information ◦ Signals use variations in the current ◦ Examples: computers, DVD players, gaming systems, etc.

 Coding system consisting of 2 choices  In electronics  2 choices is “on” or “off” ◦ The result: message represented in pulses of current Should I wear a jacket? Is it raining? Is it hot outside? Wear a light jacket Wear a raincoat Wear no raincoat NO YES

 Information that is represented in numbers, or digits  Circuit that is OFF = represented by 0  Circuit that is ON = represented by 1  Digital information is represented in long streams of digits ◦ Each 0 or 1 is also known as a bit (short for binary digit) ◦ A group of 8 bits = byte ◦ Gigabyte = 1 billion bytes (8 billion 0s and 1s)

0001; 0010; 0011; 0100; ; 0111; 1000; 1001; 1010

 Information that is represented in a continuous but varying form  Example: microphone ◦ records sound waves as analog information ◦ Sound waves vary in strength ◦ In order for signal to be burned onto a CD, its converted into digital information