Resistors + Resistance

What does the resistor color code determine?

The resistor's ohmic value and tolerance.

Fixed resistors

They only have one ohmic value which cannot be changed or adjusted. One type of fixed resistor is the composite carbon resistor.

How many terminals does a rheostat have?

Two.

Equation for voltage

V = I x R. (Voltage = Current x Resistance.)

Metal film resistors never change their _____ but are more expensive than carbon resistors.

Value.

Carbon resistors

Very popular for most applications because they are inexpensive and readily available in standard sizes and wattages.

Yellow

4.

Green

5.

Blue

6.

Violet

7.

Gray

8.

White

9.

Orange

3.

Black

0.

Brown

1.

Factors that affect the resistance of a conductor wire.

1. Length. 2. Diameter. 3. Type of conductor (material.) 4. Temperature.

Common uses for resistors in a circuit

1. Limit the flow of current. 2. Produce a voltage divider.

Red

2.

Potentiometer

A variable resistor with three terminals.

Metal film resistors

Another type of fixed resistor. These resistors are superior to carbon resistors because their ohmic value does not change with age and they have improved tolerance.

New resistor banding colors

Black = 0. Brown = 1. Red = 2. Orange = 3. Yellow = 4. Green = 5. Blue= 6. Violet = 7. Gray = 8. White = 9.

What causes damage to a resistor?

Exceeding the power rating.

Wire-wound resistors

Fixed resistors that are made by winding a piece of resistive wire around a ceramic core. These are used when a high power rating is required and for commercial purposes.

Equation for Current

I = V/R. (Current = Voltage / Resistance.)

Carbon resistors change their resistance (tolerance) with age if they are

Overheated.

Equation for Resistance

R = V/I (Resistance = Voltage / Current.)

Variable resistors

Resistors that can change their value over a specific range.

Voltage

Symbol: E or V. Unit of Measurement: Volt. Unit Abbreviation: V.

Current

Symbol: I. Unit of Measurement: Ampere (Amp.) Unit Abbreviation: A.

Resistance

Symbol: R. Unit of Measurement: Ohm. Unit Abbreviation: Ω.

The advantage of ____-_____ resistors is their high power ratings.

Wire-wound.