Resistor

A resistor adds resistance to a line of current, any medium that can resist a current (like a wire) can be treated like a resistor, resistors always absorb energy
Resistors are often the most ideal components

ideal: Ideal components do not draw current nor supply current

Symbol

The resistor is given by this symbol

Europe Standards

In Europe, resistors are defined by a different symbol

Color Code

The resistance of a resistor can be determined by using a color code system.

Color	Significant Figure	Multiply	Tolerance
Black	0	1
Brown	1	10	1
Red	2	100	2
Orange	3	1K
Yellow	4	10K
Green	5	100K	0.5
Blue	6	1M	0.25
Violet	7	10M	0.1
Gray	8	100M	0.05
White	9	1G
Gold		0.1	5
Silver		0.01	10

Ohm's Law

Ohm's Law relates voltage and current through a resistor

Ohm's Law

Ohm's Law is only meant to be used for resistors, therefore it can not be generalized to non resisting components

Root Mean Square

The root mean square gives the mean of a set of, of continuos, numbers
This is useful for measuring sine/alternating waves in AC voltages

Series vs Parallel

Resistors in series combine their resistance

Resistors in parallel divide the current between all resistors

Justification for resistors in parallel

Approximations

If then
If then

For resistors in series, the total resistance is always greater than the largest value
For resistors in parallel the total resistance is always lesser than the smallest value

Parasitic Resistor

In certain cases, the resistance of an entire circuit (in series) can be combined into a single resistor

Variable Resistor

The resistance of a resistors can be variable by shifting the contact between two points, changing the resistance

Example

An electric guitar uses variable resistors to control volume and tone

Temperature Coefficient

The temperature coefficient of a resistor is the variation in resistance given changes in temperature

Ohmeter

An ohmeter measures the resistance by measuring the voltage of a predictable current source