# What is Switches: Definition and 82 Discussions

In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of switch is an electromechanical device consisting of one or more sets of movable electrical contacts connected to external circuits. When a pair of contacts is touching current can pass between them, while when the contacts are separated no current can flow.
Switches are made in many different configurations; they may have multiple sets of contacts controlled by the same knob or actuator, and the contacts may operate simultaneously, sequentially, or alternately. A switch may be operated manually, for example, a light switch or a keyboard button, or may function as a sensing element to sense the position of a machine part, liquid level, pressure, or temperature, such as a thermostat. Many specialized forms exist, such as the toggle switch, rotary switch, mercury switch, push-button switch, reversing switch, relay, and circuit breaker. A common use is control of lighting, where multiple switches may be wired into one circuit to allow convenient control of light fixtures. Switches in high-powered circuits must have special construction to prevent destructive arcing when they are opened.

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1. ### Circuit design using switches puzzle

TL;DR Summary: I am trying to design a circuit using juat a power source, 3 switches (1,2,3) and 3 Resistors (a,b,c) and wires. i want to design the circuit so it satisfies 4 conditions. the first being if all switches are on, the 3 resistors have current flowing in parallel, second, if only...
2. ### Induced voltage in loop with multiple switches

If a current flowing within a loop is interrupted by a switch a spark occurs at some point which is a result of the built up potential across the opening switch contacts due to the stored energy in the magnetic field that was created by the flowing current. But what happens if I have a loop...
3. ### How to find the voltage threshold at which diode switches states?

I've attached pictures with the circuit and part of the attempted solution. I've replaced the diode with its offset model and obtained the equivalent circuit in the 2nd picture. After applying KVL, I've obtained that u_l=−u_D−i_D*R. Since U_D0 is greater than 0, I've deduced that the diode must...
4. ### RLC Circuit Analysis -- Two sources and two switches

Hello, this is my working. My professor did not give any answer key, and thus can I check if I approach the question correctly, and also check if my answer is correct at the same time. When t < 0, capacitor acts as open circuit, $$V(0-) = V(0+) = 9V$$ When t = infinity, $$V( ∞) = 5V$$ (because...
5. ### MOSFET Transistors as Switches

I’ve attached two images from my textbook. One describing how MOSFEET’s act like small resistances when in the triode region and open circuits when in the cutoff region, the other a list of equations describing the behavior of an NMOS transistor. I’m having trouble making sense of these two...
6. ### Electronics Switches, Pots, Displays for DIY projects - Some ideas, some questions

Many times, we might have a great idea for a DIY project/mod, but getting an interface panel together with any needed Switches, Pots, Displays, and getting them in a case can be a pain. Right now, I'm thinking about a project/mod I'd like to share with a hobby community, but many of these people...
7. ### A circuit with switches, capacitators and resistors

To solve this question first I calculated the potential energy the capacitor A stored. It's equal a: Ca.V²/2. Ok, so when switch S1 is open and S2 is closed I calculated the equivalent capacitance as if they were in series --> 1/Ceq = 1/Ca + 1/Cb --> Ceq = (Ca.Cb)/(Ca+Cb). So I used the formula...
8. ### Computer Science Student Seeks Advice on Switches & Junctions

Hi, I'm a computer science student and not an electronics guy (so I may not know stuff that an electronics guy would) but I took mechanics and E&M at the college level. I've been on here before but I don't have Facebook anymore so I created a new account with my Google. For part of my simple...
9. ### Circuit confusion, light bulbs, switches, and batteries

Before I modeled it, I thought the current would move in a figure 8 due to the battery on the right still loading the current. Then I thought of how the battery on the left would counteract that current. I am still not sure what is going on here. Is it kind of like a short circuit where the...
10. ### Controlling 10 mA Relay with Opening/Closing Switches

Can opening and closing switch turn on and off 10 ma relay
11. ### Replacing two corresponding switches as one with AND-gates

Homework Statement So this is not homework or an assignment, but usually my questions get moved here anyway. This is from a project I'm working on for my job. A user can choose between DPDT functionality (so having "SensorI" be a doorway that goes up and down, reverse) or add another sensor in...
12. ### Electronic Circuits: Capacitors and switches

Homework Statement They give the following circuit. Each capacitor is 50*10^-6 [F], the Resistors are 2[Ω], and the Voltage is 5[V]. In the first step the close only the 1st switch and let the capacitor to be charged. I've found that the charge is 2.5*10^-6 [C]. (using the equation Q = V*C)...
13. ### MHB Challenge problem #4 Is it possible for all n switches to be on at the end

$n$ lights are arranged in a circle, each operated by exactly one of $n$ switches (with each switch operating exactly one light). Flicking a switch turns the light it is operating on if it is off, and off if it is on. Initially all the lights are off. The first person comes and flicks one of the...
14. ### Engineering Electrical circuits: when all switches are closed, what is R?

Homework Statement https://pasteboard.co/Hj3g5Km.jpg When both switches 1 and 2 are closed,what is the total resistance of the set up? I couldn't figure out which resistors are connected in parallel and which resistors are actually in series in this set up when both swtiches are closed. I...
15. ### How to make a short range, remote-controlled electromagnet?

I am currently working on my high school's upcoming production of Beauty and the Beast. In the musical, there is a rose which loses petals at specific moments in the script that represent the castle's inhabitants slowly becoming less human. I figured that one of the best ways to do this remotely...
16. ### Is the textbook wrong or am I? (circuit with resistors, switches and a battery)

Homework Statement This circuit is given:[/B] Each resistor has a resistance of 30Ω, and the electrive force is 28V. Now we shut S1, and the voltmeter displays a value lower by 10% from the previous one. What is the internal resistance of the voltage source? What is the voltage between the...
17. ### How Does a Switch Affect Voltage and Current in a Circuit?

Homework Statement This circuit is given: Also: VC=18, VD=0[/B] When the switch is open, what is the voltage AB? When the switch is closed, what is VB? Homework EquationsThe Attempt at a Solution I am completely stuck, I don't really know how the switch affects the circuit. I think that...
18. ### What is the current in these 3 circuits right after the switches are opened?

Homework Statement What is the current through the resistor marked 'R' in all three circuits just after the switch is reopened after being closed for a long time? The Attempt at a Solution The explanation that we were given for (1) is that I = V/2R and (2) I = V/3R and (3) I = V/(R/2) but I...
19. ### Capacitors in a circuit with switches

Homework Statement Consider the circuit shown in the figure below, where C1 = 4.00 µF, C2 = 7.00 µF, and ΔV = 22.0 V. Capacitor C1 is first charged by closing switch S1. Switch S1 is then opened, and the charged capacitor is connected to the uncharged capacitor by closing S2. (a) Calculate...
20. ### Limit switches to control motor direction

I am trying to use two limit switches(this one) and two DPDT relays to control the direction of the motor. When the power is applied the motor should rotate one direction (direction for this question isn't important). Also, at this point (initialization) neither switch will be energized. The...
21. ### How does turning off a light bulb affect the entire electric grid?

Hello Physics Forums, this is my first post! I wanted to know how the current electrical grid system works. I mean, not in terms of creation, transmission, and distribution, but rather, how you would draw it on a circuit diagram. I understand that an AC current is generated at the power factory...
22. ### Kirchhoff's voltage law problem: Batteries, switches, resistors

Homework Statement for S1,S2,S3,S4 are all closed at the long time find the current in each resistor Homework EquationsThe Attempt at a Solution why I3 is not = i2? the solution of this question is 24-28I1-I212-12=0 7I1-32=3-----(1) 12-12I2-163=0 3I2+43=3 ---(2) I1+I2-I3=0---(3) I1=0.492...
23. ### Circuit with Four Resistors and Two Switches

Homework Statement Four resistors connected to a battery are shown in the figure (at bottom). The switch S2 is closed and switch S2 is left open. What is the magnitude of the potential difference Vcd Homework Equations Rp= Σ(1/Ri)-1 Rs = ∑Ri V = IR The Attempt at a Solution Seeing as c and d...
24. ### Length of wiring and firing switches: myth or truth?....

Tom Clancy's first novels were known for being fairly accurate from a technical/scientific point of view. That doesn't mean that they were 100% accurate, of course, but the author reportedly had some really good insider sources and knew what to ask them. I remember to have read the same thing...
25. ### Switches changing brightness of bulbs

Homework Statement All bulbs are identical, (no information given on resistance so assuming all the same) All the switches are closed and then S1 is opened, Does bulb 6 get brighter, dimmer or stay the same? Does bulb 4 get brighter, dimmer or stay the same? Explain briefly why. Homework...
26. ### Book for designing low voltage switches

Hi, Can anybody suggest a good book that discuss low voltage electrical switching hardware like circuit breakers, motor starters, automatic tranfser switches..etc? I can't seem to find any book that focuses on this.
27. ### Efficient Switch Synchronization for Remote Switches

So I got a switch here that I want to synchronize it to another switch some distance away, when I flip one of the switch on, I want the other switch to turn on as well as fast as possible with as little delay as possible. One thing I can do is to have a laser matching these two switches so when...
28. ### What is the output of a logic gate when one input is not connected?

Hello, I'm currently studying a course in digital logic. The course is included in my IT program. And I have not taken a course in electronics yet; I will later. My question basically is: what is the output of a logic gate given that one input is neither connected to a high voltage nor...
29. ### How to set the frequency of a switch in NI Multisim software

I am a new user of Multisim and I am trying to make a buck converter. In other softwares, such as pspice I was able to control the switching frequency by editing properties but in Multisim, most of the switches are user interactive. I want to set frequency of 50 Hz in a switch. Kindly help me...
30. ### Easy Guide to Installing 2 Switches for 1 Lamp: A Beginner's Tutorial

I am very bad at electrical applications. I would like to install 2 separate switches that can turn on and off a lamp. They are connected but located at 2 places. When one is switched on to turn on light, the other can also be used to turn it off later and vice versa. This is an extremely common...
31. ### Does switch's Utilization Category AC-15 include a desktop?

For reasons beyond understanding, I'm trying to source an industrial limit switch to control the power to a desktop PC. It's run on a switch mode standard computer PSU. Most of the limit switches I've looked at are rated 5 amps @ 220 VAC. But they also have an AC-15 rating usually much, much...
32. ### Connecting Heating Pad: 2 Resisters & 4 Switches

The Heating pad having 2 same value resistor and 4 single way switches (On / Off, Medium, Low,High) how do i connect those heating pad
33. ### Capacitor and Switch Potential Difference Calculations

Homework Statement The switch is initially open and the capacitors are uncharged. The applied potential difference Vab = +210V. a.) What is the potential difference Vcd? b.) What is the potential difference across each capacitor when the switch is closed? c.) How much charge flowed through the...
34. ### Unknown value of added resistor in parallel

Homework Statement Picture provided. The current going through the resistor R1 in the figure does not change whether the two switches S1 and S2 are both open or both closed. The resistances are R1 = 14.00 Ω, R2 = 142.00 Ω, and R3 = 24.00 Ω. The voltage is V = 11 V. With this information, what...
35. ### Does a CFL Pose a Fire Risk Due to Inductive Load Characteristics?

As far as I know, Compact Fluorescent Lamp (CFL) is an inductive load. I understand that inductive load doesn't allow an immediate change in current. When the circuit was initially open (through open switch) then became close, the inductive load was energized. So opening again the circuit after...
36. ### Question about Inductors and Switches

Homework Statement The switch has been open for a very long time, and then we close it. In the instant right after we close the switch, assuming that...
37. ### Help in trying to build microcontroller powered Chess Board

Hello all, as the title states I'm trying to build an arduino powered chess board. The chess pieces will have magnets on the bottom and each square of the board will be equipped with a reed switch for detecting the presence of the magnetic field produced by the magnet. I recently tried this out...
38. ### How Do Switch Operations Affect Capacitor Behavior in a Circuit?

Homework Statement Consider the circuit shown below. Use this circuit for both parts of this question. Be sure to answer both parts! https://www.physicsforums.com/attachment.php?attachmentid=67797&stc=1&d=1395204781 Both capacitors are originally uncharged and both switches are open. S1...
39. ### SPDT switches in CMOS processes.

Hi guys, Recently I had to design a SPDT switch for a project, which I was able to design using the trivial circuit with 2 transmission gates and 1 MOS inverter, like this: http://www.semicon.toshiba.co.jp/eng/product/new_products/logic/1326183_37648.html I think that this circuit is not...
40. ### Boolean Rings: System of Switches.

Okay, So I just got done reading and re-reading Chapter one of Introductory Real Analysis by Andrei Kolmogorov and S.V Fomin, I have to say it is a lot easier to read than the symbolic logic book I have. But to the point, There is this section which talks about Boolean Rings and it defines them...
41. ### Quick question about make before break switches and capacitors

Homework Statement A capacitor is initially connected to a voltage source in series for a long time. At time t0 the make before break switch switches to another series circuit which includes the capacitor. This means that the capacitor will have an initial voltage v(0-) = voltage source...
42. ### Switches - preset/clear features

I have attached the switch. I thought I understood the 3 problems, until I got to question 35. My textbook says that the clear feature overwrites any input and sets the output to 0. So that seems to be the case with 33 and 34. But why not question 35?
43. ### What kind of power MOSFET switches are available in the market?

are there any power MOSFET switches that are largely commercially available in the market today? with more than blocking voltage 120 volts at OFF state, ability to conduct more than 30 amperes when in ON state, controling load of over 2500 watts? and in the cost of at least 40 dollars?
44. ### Power electronic switches VS dc contactor

As we know the contactor in power circuit make spark when it open and so its contacts may damage and aging Is it possible to replaace the contactor by power electronics switches such as MOSFET TRIAC and IGBT? Any help will be appreciated
45. ### PWM, Limit switches, and TX's / RX's

Hey everyone. I am a total noob to electronics, so I would really appreciate your help on my first engineering project! I am building an RC Excavator and need help with the circuits for the linear actuators I plan to build. I have 3 DC motors on the way with a voltage range from 6-12V. I have...
46. ### Freedom or aligators use switches for code.

I was wondering if anyone had seen this logic problem in a different form or knows how a solution to this. Thanks Freedom or Alligators Once upon a time, a prison warden was responsible for 22 prisoners on Death Row. These prisoners were students who had done terrible things: some illegally...
47. ### What number on a digital clock draws the least current from a battery?

Homework Statement There is a circuit with 7 LEDS connected in parallel, each with a switch on its parallel. There is a battery supplied. The LEDS correspond to those of a digital clock for example the number 8 would light up all 7 LEDS, whilst the number 0 would light up 6 LEDS. Which...
48. ### If light hits a mirror and then switches direction

if light hits a mirror and then switches direction... if light hits a mirror at a 90 degree angle, wouldn't it HAVE to travel slower than the speed of light when it hit the mirror?
49. ### Circuits / Switches / Currents -TRUE FALSE QUESTIONS (Pic included)

Circuits / Switches / Currents --TRUE FALSE QUESTIONS (Pic included) Homework Statement Homework Equations The Attempt at a Solution I really have no idea, on going about solving this as I don't have my book with me and the homework is due in a few hours. I'm sure if brief...
50. ### Parallel transmission lines / TL switches

If i wanted to make a 1:N coaxial RF switch (say ~100MHz, nothing too high), could you simply route N traces in a star pattern on a PCB and implement a mechanical switch to either connect to your measurement point, or terminate in the characteristic impedance (say 50 Ohm). I'm getting thrown...