1 RC circuits You would like to make a simple timer that will sound a buzzer one minute after a switch in an RC circuit is closed. You design a buzzer so that it will sound when the charge on a capacitor falls below 20% of it's initial value. You are using 200nF capacitor. How large of a resistor do you need? www R

1 RC circuits You would like to make a simple timer that will sound a buzzer one minute after a switch in an RC circuit is closed. You design a buzzer so that it will sound when the charge on a capacitor falls below 20% of it's initial value. You are using 200nF capacitor. How large of a resistor do you need? www R

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter20: Capacitance In Ac Circuits

Section: Chapter Questions

Problem 7PP: A pure capacitive circuit is connected to a 480-volt, 60-Hz power source. An ammeter indicates a...

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You are an electrician working in an industrial plant. You discover that the problem with a certain machine is a defective capacitor. The capacitor is connected to a 240-volt AC circuit. The information on the capacitor reveals that it has a capacitance value of 10 mF and a voltage rating of 240 VAC. The only 10-mF AC capacitor in the storeroom is marked with a voltage rating of 350 WVDC. Can this capacitor be used to replace the defective capacitor? Explain your answer.
Three capacitors having capacitance values of 20F,40F, and 50F are connected in parallel to a 60 - Hz power line. An ammeter indicates a circuit current of 8.6 amperes. How much current is flowing through the 40F capacitor?
You are working in an industrial plant. You have been instructed to double the capacitance connected to a machine. The markings on the capacitor, however, are not visible. The capacitor is connected to 560 volts and an ammeter indicates a current of 6 amperes flowing to the capacitor. What size capacitor should be connected in parallel with the existing capacitor? What is the minimum AC voltage rating of the new capacitor? What is the minimum DC voltage rating of the new capacitor? What is the minimum KVAR size that can be used in this installation?
You are a journeyman electrician working in an industrial plant. Your task is to connect an inductor to a 480-V, 60-Hz line. To determine the proper conductor and fuse size for this installation, you need to know the amount of current the inductor will draw from the line. The nameplate on the inductor indicates that it has an inductance of 0.1 H. An ohmmeter reveals that it has a wire resistance of 10 . How much current should this inductor draw when connected to the line?
A capacitor uses air as a dielectric and has a capacitance of 3 F. A dielectric material is inserted between the plates without changing the spacing, and the capacitance becomes 15 F. What is the dielectric constant of this material?
You find that a 25-F capacitor connected to 480 VAC is defective. The storeroom has no capacitors with a 480-VAC rating. However, you find two capacitors rated at 50 F and 370 VAC. Can these two capacitors be connected in such a manner that they can replace the defective capacitor? If yes, explain how they are connected and why the capacitors will not be damaged by the lower voltage rating. If no, explain why they cannot be used without damaging the capacitor.
A postage stamp mica capacitor has the following color marks starting at the upper left dot: yellow, violet, brown, green, no color, and blue. What are the capacitance value, tolerance, and voltage rating of this capacitor?
4. In what form is the energy of a capacitor stored?
Inductive Circuits Fill in all the missing values. Refer to the following formulas: XL=2fLL=XL2ff=XL2L Inductance (H) Frequency (Hz) Inductive Reactance ( ) 1.2 60 0.085 213.628 1000 4712.389 0.65 600 3.6 678.584 25 411.459 0.5 60 0.85 6408.849 20 201.062 0.45 400 4.8 2412.743 1000 40.841
A pure capacitive circuit is connected to a 480-volt, 60-Hz power source. An ammeter indicates a current flow of 24 amperes. The circuit current must be reduced to 16 amperes by connecting a second capacitor in series with the first. What is the value of the existing capacitor? What value capacitor should be connected in series with the original capacitor to limit the circuit current to 16 amperes?
For the following circuit, do the following:a) Write the mathematical expressions for the voltage VC, VR1 and IC if the switch is on theposition 1.b) Find the voltage VC, VR1 and IC if the switch changes to a position 2 at t = 100ms.c) Determine the discharge time of the capacitor.d) Draw the charge and discharge waveforms.
Find the numerical value of the capacitance per unit length of two long parallel wires (both parallel to the x axis in the xy plane), each with radius 1 mm, with their centers separated by 4 mm. Express your answer in picofarads per meter. You may assume the wires are perfect conductors.