Polarity Definition and 164 Threads

Electrical polarity is a term used throughout industries and fields that involve electricity. There are two types of poles: positive (+) and negative (−). This represents the electric potential at the ends of a circuit. A battery has a positive terminal (+ pole) and a negative terminal (− pole). Interconnection of electrical devices nearly always require correct polarity to be maintained. Correct polarity is essential for the operation of vacuum tube and semiconductor devices, many electric motors, electrochemical cells, electrical instruments, and other devices.

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  1. MadMax_8228

    Can the polarity at the 2 ends of a solenoid be the same in normal conditions?

  2. fmorgan2

    B Changing magnetic polarity of an electromagnet

    I would like to change the polarity of an electromagnet. I have reversed the wires attached to a 9 volt battery that wound about a bar magnet but this did not seem to make the north pole become the south pole. Thanks for your assistance, Frank
  3. yucheng

    Why are more polarized bonds weaker (Acid dissociation)?

    Wikipedia says that: The weak acidity in dilute solution is sometimes attributed to the high H—F bond strength, which combines with the high dissolution enthalpy of HF to outweigh the more negative enthalpy of hydration of the fluoride ion. (https://en.wikipedia.org/wiki/Hydrofluoric_acid) (the...
  4. M

    Electromagnet Polarity Switching for Reversed Motion

    I am trying to understand the differences in design between a traditional solenoid with a ferrous plunger vs linear motors that use either induction or permanent magnets. From my understanding, a traditional solenoid, whether DC or AC, cannot fire in both directions with polarity switching since...
  5. P

    Solubility depends on polarity or on the number of hydrogen bonds?

    Does solubility depend on the polarity of the molecule or on the number of hydrogen bonds that are formed with water? For example: CF4 can form hydrogen bonds, but it's not polar. Glucose Is Polar e can form hydrogen bonds. How can I predict solubility? Thanks
  6. D

    Why are my terminals not marked on my capacitor?

  7. O

    Polarity of Propan-1-ol and Propan-2-ol

    Based on the two structures, I think Propan-1-ol is more polar because the electrons are drawn to the end of the molecule while propan-2-ol has electrons drawn to the center of the molecule (less of an unequal electron distribution in the molecule). However when looking at the dipole moment I...
  8. garthenar

    Engineering Cadence Transformer dot convention and polarity (xfmr)

    Here is the circuit... Here is my work so far in cadence (I haven't put in values for other components in because the moment I saw the dot convention I started trying to figure that out). Where I'm at -There apparently isn't a way in Cadence Virtuoso (the program my class uses) to change the...
  9. A

    Why does the polarity of a bass guitar recording vary?

    Sorry if this is the wrong place for this question. I am a musician and recording engineer trying to learn about why my bass guitar recordings sometime appear with the waveform going up first (positive polarity) and other times going down first (negative polarity) in my DAW (digital audio...
  10. gonadas91

    A Positive polarity of a retarded Green's function's imaginary part

    Hi all! I am currently working on a problem that involves calculation of Green functions. I am having serious doubts on some part of the calculation, as I am getting a GF that has positive values of its imaginary part. According to Lehman's rule, the retarded GF can be decomposed by the spectrum...
  11. S

    Sudden polarity reversal in opposing permanent magnets?

    Hi all, I'm working with a pair of multi-pole neodymium ring magnets (rated ~119lbF) and finding that if the opposing poles are forced together, with the magnets in alignment, that at very close range (may be a millimeter or two apart?) the two magnets will suddenly snap together as if one has...
  12. C

    Does Polarity and Current Direction Affect Energy Flow in AC Circuits?

    I assume that because there is a resistance, the polarity of the voltage must be the same as the charge flow, and thus the current, in order for energy to flow in the same direction. For instance, could I use the example of a light bulb (the resistor) plugged into AC lines; we know that if the...
  13. jerromyjon

    High voltage coil discharge polarity for vehicle spark plugs

    I've recently had a discussion with fellow technicians in the automotive industry about spark plugs and some systems having "opposite polarity" on the ignition coils. (specifically the secondary coil which sends the high voltage pulse to the plug which sparks the fuel) Common sense tells me...
  14. H

    Why is the correct polarity important with AC?

    Hi! I was watching some random videos about electricity on you youtube and then got this question: if AC changes direction constantly (50 times per second) then why is it still important to connect live to live and neutral to neutral in wall outlets? For example some wall outlets have different...
  15. fight_club_alum

    Determining the voltage polarity of the independent current source

    I am so sorry if I am posting this in the wrong forum; it is just not a homework problem, and I can't find the right place - it's more of a study help question.
  16. E

    Solve Vo: Voltage Nodal Analysis w/ KCL Equation

    I'm asked to solve for Vo for this equation. I've set the bottom node to be my reference node before applying nodal analysis. When included in the KCL equation for node at Vb, will the dependent voltage source 20iΔ be negative since the current through that element is leaving node C? Say, the...
  17. M

    Question about the polarity of a voltage (PHY 2 for engineers)

    My problem is understanding how the polarity of a voltage makes sense. For example, In my textbook, its states that "batteries move negative charges from its negative terminal to its positive terminal. In terms of potential, the positive terminal is at a HIGHER voltage than the negative...
  18. Brett Anthony

    Batteries in Parallel, One Reverses Polarity

    So, some time after getting a new car the batteries on my FOB died. So I went in and replaced them, two CR2016's was all that was needed (on top of each other in parallel). No more than a month later I noticed the battery felt like it was dying already (light not as strong, delay on the actions...
  19. K

    B LC Oscillation: Current Flow & Charge Polarity

    when in LC oscillation current flow from inductance to capacitor and charge is opposite polarity. why don't current flow in reverse of it and charging the capacitor in same manner as it was earlier.
  20. A

    Polarity and solubility of AgCl

    Hi everyone. I am a beginner in chemistry (introductory) so my knowledge is pretty limited when it comes to this subject. From what I have been taught, like dissolves like, meaning polar dissolves polar and non-polar dissolves non-polar. The electronegativity difference of AgCl is around 1.3...
  21. A

    Polarity of magnetic field in a conducting wire

    When current flows through a copper wire, for example, a magnetic field is produced. What is the polarity of that field? I've seen an example with special relativity and how a positive charge would be deflected. Does that mean the field is negative to a stationary object? Every video I watch...
  22. L

    Understand AC Transformer Polarity for Three-Phase Connections

    my transformer book does not cover an area i am interested in and was wondering if someone would direct me to literature that would help me understand something and if you wouldn't mind trying to explain it to me yourself that would also be appreciated. you have three single phase transformers...
  23. K

    Relation of Charge polarity and voltage polarity

    Homework Statement What is the relationship of charge polarity and voltage polarity? I understand an anion has negative charge and cation ion has negative charge, but does an anion have a positive voltage and the cation have a negative voltage? Given the above is generally true, when is the...
  24. MrGenetic

    Is there a relationship btw ionizable and polarity?

    While polar molecule solved in solution, is this refers to ionizable molecule? Is it necessary or is it different things according the definitions?
  25. B

    Electromagnet polarity switching....

    I regret I know nothing about subject but wonder if anyone could advise where I could obtain a device (including magnets) which will change the polarity of two electro magnets from once per second to hundreds of times per second?
  26. U

    How rubbing a needle on a magnet affects its polarity

    Homework Statement It is known that when rubbing a needle on a magnet, the needle will become magnetized. If you rub the needle on the north side of the magnet, will it point differently than if you rubbed it on the south side of the magnet? Does it matter what direction you rub the needle...
  27. J

    Polarity of an Electromagnetic Wave

    I have asked a form of this question previously: https://www.physicsforums.com/threads/electromagnetic-waves-and-polarity.857347/ ...but have come back to it in slight confusion. Say I have this antenna and the voltage source is increasing with a constant acceleration of its voltage. It...
  28. Emmanuel_Euler

    Dielectric Constant Vs Temperature Vs Polarity

    please explain the concept of dielectric constant in the simplest CHEMICAL terms possible. why does it decrease when the temperature increases? and why does it increase when the polarity increases? please keep it simple and brief.
  29. D

    Simple test using current values to prove polarity

    I work in a large electrical machine shop. We have a test that no one can explain to me. We energise a dc field frame (in this case 6 pole) with ac and record the current draw, then reverse the polarity of connection, energise and compare values. If a pole is reversed polarity then a difference...
  30. C

    What is the worst problem caused by reversing the polarity?

    Reversing the polarity is a mainstay of science fiction but what is the worst example of incorrect wiring putting the negative into positive and reverse leading to serious electrical problems.
  31. R

    What is the Polarity of Charges in a Millikan Type Experiment?

    Homework Statement : [/B]. in a milikan type experiment there are two oil droplets P and Q between the charged horizontal plates, as shown in the figure. Droplet P is in rest while Q is moving upwards. The polarity of charges on P and Q is: P. Q a). +. + b)neutral. -...
  32. M

    Polarity Reversal: Why Is Voltage of Right Source Negative?

    Homework Statement Why is the voltage of the right source negative? Homework Equations The Attempt at a Solution I learned that a circuit element is positive or negative, because of the terminal with respectively the highest or lowest voltage. So, if the positive terminal has a lower...
  33. T

    Is the covalent character of sodium chloride affected by its polarity?

    I found out that sodium chloride has a dipole moment of 9 debye, and a sodium-chlorine distance of .28 nm. When I divide one by the other, I get 2/3 of an electron. Did my math go wrong somewhere, or is this supposed to happen? I expected something close to a full elementary charge.
  34. A

    Polarity of capacitor/inductor in RLC circuit

    Homework Statement In the figure given, the switch was at position A for a long time, at time =0 the switch is turned to position B... My question is how do we assume the polarities for both the resistor and the capacitor after the switch is in position B Homework Equations ?? The Attempt at...
  35. V

    When Should Electronegativity and Molecular Shape Be Considered?

    Homework Statement When to use electronegativity value? and when to look at both bonds and shape? Homework EquationsThe Attempt at a Solution This isn't really a question more so need some clarification. First question is about electronegativity and bond polarity. When placing the delta...
  36. L

    Question about voltage polarity and power

    Hello, If a positive charge is moved from point b to a, then we say a is positive to point b, and assign negative polarity to point b. If a negative charge is moved from a to b, we still say the same. Why? Please explain in simple terms if possible. Another question, if current and voltage...
  37. T

    Confused about inductor polarity

    So initially S1 and S4 are closed and current flows as seen above. After some time S1 and S4 are open and current flows as seen above. Now I am confused about the polarity of the inductor, what if I said the current flows through D1 and D4 instead of D3 and D2 ?, would that be wrong ?
  38. kostoglotov

    Why are these capacitor voltages opposite polarity?

    Homework Statement imgur link: http://i.imgur.com/JETj0Cq.png Homework Equations V_L = L\frac{dI_1}{dt} V_L + V_1 + V_2 + V_{R1} = 0 The Attempt at a Solution [/B] Just using basic KVL, shouldn't V_L = -V_2 - V_1 - V_{R1} and so therefore we should get \frac{dI_1}{dt} = \frac{-V_2 -...
  39. matrow

    Programmable polarity reversal circuit

    Hi so I am a Civil engineering student with very little knowledge in circuits so I apologize if this question is redundant or common. I am trying to apply a current through a soil sample in order to consolidate it faster using Electro-Osmosis. Polarity Reversal should theoretically speed the...
  40. RoboNerd

    Chemistry How Does Methyl Orange's Color Intensity Vary on Cotton, Nylon, and Wool?

    Homework Statement I have a methyl orange molecule. Then my problem says that "wool is a protein, a naturally occurring polymer made up of amino acids with ionized side chains. cotton is a naturally occurring polymer made up of glucose units with hydrophillic groups surrounding each glucose...
  41. Sollicitans

    Do resistor polarity assignments affect current flow in Kirchoff's second law?

    I guess there's a simple rule, but I can't find it anywhere and it seems I was supposed to know this. I'll appreciate it if someone explains me how it works and also if (and how) is related to the way you consider positive and negative voltages when you apply Kirchoff's second law as shown in...
  42. goonking

    Why do resistors have polarity?

    Homework Statement When I took intro physics, resistors didn't have polarity. Now, in electrical circuits class, we start seeing resistors with polarity. For example, this diagram in our textbook: My professor insist that this problem had a misprint/typo: the polarity on the 2 ohm resistor...
  43. B

    High voltage charge & same polarity on two concentric rings

    I have a charged ring with a high voltage potential. As I see it the charges repel from each other and so position themselves around the outside of the ring. I want to push the charge to the inside surface of the ring and so I envisioned a 2nd ring positioned concentrically just outside this...
  44. J

    Electromagnetic waves and polarity

    Say you have a transmitting whip antenna. If you send a quick DC burst into it, you will get the electrons in the antenna accelerating in one direction like this: If that EM wave is then absorbed by a receiving whip antenna, the electrons will also move in one direction. The polarity of the EM...
  45. Robsta

    Investigating the water-ice electret

    Hello all, I'm going to investigate the properties water when frozen in a strong electric field for a product I'm designing. A strong field will align the polar water molecules, and then they will freeze. I'm planning to create this strong field with a car battery attached to two parallel...
  46. Aristotle

    Engineering KVL for a RLC circuit given current direction and polarity o

    Homework Statement KVL for a RLC circuit given current direction and polarity of a resistor? Here is the diagram of the circuit: Homework Equations KVL Sum of voltages equal zero The Attempt at a Solution I am actually looking for the voltage across the inductor (VL), so I decided the...
  47. K

    Giancoli Physics Book -- confused at meaning of "test charge" polarity

    In the giancoli physics textbook for engineers and scientists, it says "E=F/q where E is the force on a small positive test charge at rest..." Then about one paragraph later it proceeds to say "If q is positive, F and E point in the same direction. If q is negative, F and E point in opposite...
  48. F

    Polarity of back EMF in an inductor....

    Hello Forum, the law of electromagnetic induction states that a time-changing current causes a back (counter) emf in an inductor. The back emf opposes the change in current by generating an induced current I_ind. If dI/dt>0, the induced current is opposite in direction to the main changing...
  49. Tam Le

    Polarity of Water: Exploring Electrical Neutrality

    I understand that, in the molecule H2O, O has a slight negative charge while the two H's have a slight positive charge. However, I do not understand why the molecule as a whole is considered electrically neutral. Also, how is electrically neutral defined? Does it mean that the electrical...
  50. J

    AC and polarity of hot and neutral wires

    I'm a bit confused as to how only one wire changes it's polarity in an alternating circuit. I also checked out a previous thread (https://www.physicsforums.com/threads/how-can-polarity-of-ac-inverse-but-keep-the-live-hot-and-neutral-cold.752605/) and didn't find a sufficient answer. I found this...
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