CAPACITANCE Benchmark Companies Inc PO Box 473768 Aurora CO 80047

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<ul><li> Slide 1 </li> <li> CAPACITANCE Benchmark Companies Inc PO Box 473768 Aurora CO 80047 </li> <li> Slide 2 </li> <li> DEFINED The device used in electronics for storing this charge is called the capacitor. Capacitance is the measure of how much electrical charge a device can store. Capacitance is measured in Farads (F) </li> <li> Slide 3 </li> <li> DEFINED Schematic Symbols Non-polarizedElectrolyticVariable </li> <li> Slide 4 </li> <li> CAPACITOR CODE Ceramic Disc Capacitors have a code that shows their value 100,000 F or.1uF The number you obtain is in picofarads. Determine the value of the capacitor by utilizing this general method </li> <li> Slide 5 </li> <li> THEORY +++ - - - The capacitor is made from two metal plates with an insulator type material in the center called a dielectric. When power is applied to the circuit the capacitor will attract electrons to plate A. Charging </li> <li> Slide 6 </li> <li> THEORY +++ - - - The electrons can not pass through the dielectric so the plate starts storing electrons. The electrons on plate B are repelled from plate A and attracted to the power source leaving the plate positively charged. This process lasts until the capacitor has been fully charged. Charging </li> <li> Slide 7 </li> <li> THEORY Once the capacitor is charged it may now be used to power a consuming device. There is one limitation. The device can only be powered as long as the charge is in the capacitor. The electrons on plate A will attract to plate B once there is a path for them to flow. Once all the electrons have been neutralized, the capacitor has lost all of its charge. Discharging +++ - - - </li> <li> Slide 8 </li> <li> RATING CAPACITORS Capacitors are rated in Farads and Volts - One farad is equal to 1amp being charged by an EMF of 1volt per second. The formula is shown below. C = Capacitance in Farads I = Current in amps E=Voltage in volts t=time in seconds -Typically capacitors are in Microfarads (F) or Picofarads (pF). -The voltage rating is a working rating the capacitor can handle before being damaged. </li> <li> Slide 9 </li> <li> CAPACITORS IN SERIES The total capacitance in a series circuit adds up inversely just as resisters do in parallel. </li> <li> Slide 10 </li> <li> CAPACITORS IN PARALLEL The capacitance of capacitors in parallel work like resistors in series. The capacitance of each of the capacitors add up to the total capacitance of the circuit. </li> <li> Slide 11 </li> <li> CAPACITOR TYPES Ceramic Disc Electrolytic Radial Lead Axial Lead Variable Capacitor Polyester Film </li> <li> Slide 12 </li> <li> CERAMIC DISC CAPACITORS Ceramic Disc Capacitors are named for the material that make up the dielectric. Ceramic Disc capacitors are rounded in shape and are usually a light brown color. The advantage to the Ceramic Disc capacitor is that it can work at small capacitance and high voltages. </li> <li> Slide 13 </li> <li> ELECTROLYTIC CAPACITORS Electrolytic Radial Lead Axial Lead Electrolytic Capacitors are capacitors that have their plates polarized. One plate is positive and one negative. It is very dangerous to reverse the polarity of an electrolytic capacitor and should not be done. Electrolytic capacitors can handle very large capacitances for their size. </li> <li> Slide 14 </li> <li> ELECTROLYTIC CAPACITORS Electrolytic Radial Lead Axial Lead These capacitors look like tin cans and their leads can be radial or axial. The rating of these devices is easily read on the device itself - no code. The rectangular shape in the lightly shaded area on the capacitor indicates which lead is negative. On the axial capacitor an arrow points to the negative lead. </li> <li> Slide 15 </li> <li> VARIABLE CAPACITORS Variable Capacitor Variable Capacitors are used in tuning circuits. The capacitor can be used as a filter in order to tune in a specific frequency. </li> <li> Slide 16 </li> <li> OTHER CAPACITORS Polyester Film There are many other types of capacitors. Their names come from the material that makes up the dielectric. The ratings for these capacitors are usually labeled on the device. Mylar Polypropylene Film Chip Capacitor Tantalum </li> <li> Slide 17 </li> <li> RC TIME CONSTANT The RC Time Constant in the time it takes, in a series resistor capacitor circuit, for voltage to rise to 63.2% or fall to 36.8% of the peak voltage value of the circuit. When five of these time constants occur, the capacitor will be fully charged. The formula below can be used to predict this value. t = Time in seconds R = Resistance in Ohms C = Capacitance in Farads </li> <li> Slide 18 </li> <li> RC TIME CONSTANT example With a 1k resistor and a 1F capacitor placed in series, what is the time constant of the circuit and how long will it take to fully charge the capacitor? Full Charge Time = 1ms x 5 Full Charge Time = 5ms Capacitor Fully ChargedTime Constant Calculation t =RC t=1k x 1F t =1000 x.000001F t=1ms </li> <li> Slide 19 </li> <li> The first cursor proves that at 1ms the voltage is 6.32V The second cursor is showing that after 5 time constants the capacitor is fully charged. RC TIME CONSTANT GRAPHIC REPRESENTATION </li> <li> Slide 20 </li> <li> USING A MULTIMETER Some Multimeters can read the capacitance of capacitors. Place the capacitor in the holes as shown in the figure to the right. Set dial for the F(Farads) setting then read the screen. Change range if necessary. The capacitor below is.02uF. </li> <li> Slide 21 </li> <li> End of Presentation </li> </ul>

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