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