Resistors Flashcards
Can a variable resistor be wire wound?
Yes, some rheostats and potentiometers are wire wound.
Resistors commonly have three ratings; if legible, how are these displayed?
- Resistance: uses a letter code to indicate decimal position and multiplier.
- Power: simply measured in watts. Determined by physical size if not displayed on compound and film resistors.
- Tolerance: given as a percentage range.
What is the colour order of resistor marking bands from 0-9?
- Black
- Brown
- Red
- Orange
- Yellow
- Green
- Blue
- Violet
- Grey
- White
What is the typical resistance range of dry skin?
100 000 - 600 000 Ohms
What are the two categories of resistors?
What are the sub categories of these?
- Fixed
- Film
- Composition
- Wire wound
- Variable
- Rheostat
- Potentiometer
How are composition resistors constructed?
Normally a carbon based alloy with a binder ( used to hold resistive material together) formed into a cylindrical shape, complete with wire leads and a protective coating (ceramic silicone or lacquer based).
Can a potentiometer act as a rheostat?
Yes, if one terminal is shorted out or not used.
What does the power rating of a resistor signify?
The rate at which the resistor can convert electrical energy into heat and not overheat.
If a gold or silver band is used as a multiplier band in a resistor, how must one multiply?
- Gold = x 0.1
- Silver = x 0.01
If a red band is used as a tolerance band, what will the tolerance be?
2%
Should a resistor ever get too hot to touch?
It can. E.g. An incandescent lamp.
When should wire wound resistors be used?
In high power rating applications.
When reading the colour bands of resistors, the bands should be placed closest to the…?
Left end.
