Introduction to Resistors
Online Resource for ETCH 213
Faculty: B. Allen
Ratio
A relationship in quantity, amount, or size between
two or more things.
3/2 Ratio as a fraction
3:2 Ratio using ratio sign
1.5 to 1 Ratio as a decimal
Online Resource for ETCH 213
Faculty: B. Allen
Rounding off
Rule: When the first digit to be dropped is a 6
or more, or a 5 followed by a digit that is more
than zero, round up. When the first digit to be
dropped is a 4 or less, or a 5 followed by a zero,
do not change the previous digit.
Online Resource for ETCH 213
Faculty: B. Allen
Significant places
3.49
3 significant places
34,900
3 significant places
34.90
4 significant places
0.000349
3 significant places
Online Resource for ETCH 213
Faculty: B. Allen
Percentages
% means 0.01
10% = 10 × 0.01 = 0.1
250% = 250 × 0.01 = 2.5
3.5 = 3.5/0.01% = 350%
Online Resource for ETCH 213
Faculty: B. Allen
Bar graph
90
80
70
60
East
West
North
50
40
30
20
10
0
1st Qtr
2nd Qtr
3rd Qtr
Online Resource for ETCH 213
Faculty: B. Allen
4th Qtr
Circle graph
1st Qtr
2nd Qtr
3rd Qtr
4th Qtr
Online Resource for ETCH 213
Faculty: B. Allen
Average
n
∑
1
n
= Average
Online Resource for ETCH 213
Faculty: B. Allen
Resistor
Resistor – Component made of a material that
opposes the flow of current and therefore has
some value of resistance.
Online Resource for ETCH 213
Faculty: B. Allen
Fixed value resistors
Fixed-Value Resistor – A resistor whose value
cannot be changed.
Carbon Composition Resistor – A fixed resistor
consisting of carbon particles mixed with a binder,
which is molded and then baked.
Dissipation – The release of electrical energy in the
form of heat.
Wattage Rating – Maximum power a resistor can
safely handle continuously.
Online Resource for ETCH 213
Faculty: B. Allen
Carbon film Resistors
Carbon Film Resistor – Thin carbon film deposited on a
ceramic form to create resistance.
Online Resource for ETCH 213
Faculty: B. Allen
Metal Film Resistor – A resistor in which a film of metal,
metal oxide, or alloy is deposited on an insulated substrate.
Wirewound Resistor – A resistor in which the resistive
element is a length of high-resistance wire or ribbon, usually
nichrome, wound onto an insulated from.
Online Resource for ETCH 213
Faculty: B. Allen
Packaging
Single In-Line Package (SIP) – Package
containing several electronic components
(generally resistors) with a single row of
external connecting pins.
Dual In-Line Package (DIP) – A package having
two (dual) sets or lines of connecting pins.
Online Resource for ETCH 213
Faculty: B. Allen
Variable resistor
Variable Resistor – A resistor whose value can be changed.
Rheostat – Two terminal variable resistor that, through
mechanical turning of a shaft, can be used to vary resistance.
Online Resource for ETCH 213
Faculty: B. Allen
Potentiometer
Potentiometer – A three-lead variable resistor that, through
mechanical turning of a shaft, can be used to produce a
variable voltage of potential.
Online Resource for ETCH 213
Faculty: B. Allen
Thermally (heat) adjustable
variable resistor
Bolometer – A device whose resistance changes when
heated.
Resistive Temperature Detector (RTD) – A
temperature detector consisting of a fine coil of
conducting wire that will produce a relatively linear
increase in resistance as temperature increases.
Thin-Film Detector (TFD) – A temperature detector
used for very precise temperature readings
Online Resource for ETCH 213
Faculty: B. Allen
Optically (light) adjustable
variable resistor
Photoresistor – A device whose resistance
varies with the illumination of the cell.
Online Resource for ETCH 213
Faculty: B. Allen
Measuring resistance
Ohmmeter – Measurement device used to measure electric
resistance.
Online Resource for ETCH 213
Faculty: B. Allen
Resistor color coding
Online Resource for ETCH 213
Faculty: B. Allen
Power dissipation due to
resistance
P=V×I
P = I2 × R
P = V2/R
Online Resource for ETCH 213
Faculty: B. Allen
Filament resistor
Filament Resistor – The resistor in a light bulb or electron
tube
Incandescent Lamp – An electric lamp that generates light
when an electric current is passed through its filament of
resistance, causing it to heat to incandescence.
Cold Resistance – Resistance of a device when cold
Hot Resistance – Resistance of a device when hot due to heat
generated by electric current
Ballast Resistor – A resistor that increases in resistance when
current increases. It can therefore maintain a constant current
through the circuit.
Online Resource for ETCH 213
Faculty: B. Allen
Testing resistor
An ohmmeter sends a small current through a
resistor to measure a voltage drop when
measuring resistance.
Online Resource for ETCH 213
Faculty: B. Allen
This concludes
Introduction to Resistors
Online Resource for ETCH 213
Faculty: B. Allen