AY Honors/Radio Electronics/Answer Key
Radio Electronics
Identify at least 20 symbols used in electronics.
Identify the value of resistors by the color code
The value of a resistor is marked on the device itself by using bands of colors. The color code assigns a number to each of the following colors:
- 0 - black
- 1 - brown
- 2 - red
- 3 - orange
- 4 - yellow
- 5 - green
- 6 - blue
- 7 - violet
- 8 - grey
- 9 - white
Note that after black and brown, the next six colors are arranged as they are found in the rainbow. These colors can also be memorized by the use of a mnemonic such as "Black Bears Run Over Yellow Grass, But Vultures Glide over Water."
Two other colors are used to specify the tolerance of the resistor - that is, how close the actual value is to the value encoded on it:
- 5% - gold
- 10% - silver
If there is no gold or silver band, the resistor has a 20% tolerance.
Remember that just as "gold is better than silver," a 5% (gold) resistor is better than a 10% (silver) resistor.
On a four-band resistor, the third band represents the number of zeros that follow the first two digits, and the fourth band represents the tolerance. So a brown-black-red-gold combination would indicate a 1000 Ohm resistor with a 5% tolerance.
Resistors with tighter tolerance are usually specified with three bands indicating the numeric value and a fourth indicating the number of zeroes following.
Demonstrate proper soldering techniques
Explain the use and operation of various important components in electronics such as resistors, variable capacitors, fixed capacitors, coils, transistors, integrated circuits, diodes, and transformers.
Know and understand Ohm's Law.
If a voltage is applied across a resistor, current will flow through it. Ohm's law describes the relationship between this current, voltage, and resistance. It can be written as
[math]\displaystyle{ v = i r }[/math]
Where v is volatage (measured in volts), i is current (measured in amps), and r is resistance (measured in ohms). The equation can also be written as
[math]\displaystyle{ i = v/r }[/math]
and
[math]\displaystyle{ r = v/i }[/math]
Basically, it means that if the voltage is held constant and the resistance is decreased, the current is increased. Or if the resistance is held constant and the current is increased, the voltage will also increase.
