What is Polarity: Definition and 164 Discussions

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. H

    O vs P ChloroNitroBenzene Polarity

    I'm having trouble understanding the difference in polarity between O and P ChloroNitroBenzene for my lab. One group is telling me the O isomer is less polar because the nitro group and chloro group do intramolecular bonding preventing intermolecular bonding. Another group is telling me the O...
  2. J

    Polarity of magnets, Simple?- confused me.

    I don't get it, is the north pole of a magnet the north seeking; having in mind that like poles repel? Please help.:confused:
  3. M

    Possible Errors Made Regarding Polarity and Intermolecular Bonds

    Hello, I wouldn't necessarily regard this as homework. While these are errors I believe I have found within an online course in which I am currently enrolled, my asking is simply carried out with interest in acquiring an accurate knowledge of entry-level chemistry. While studying polar...
  4. M

    Is there a difference in polarity for sonar sensors?

    Hello, for my robot project, I'm using a system of of sonar range finding sensors which are generally used for this type of thing. My question is of there polarity. I'm assuming that it does not matter, for there are no clear indicators of positive or negative values on any of the poles. here...
  5. Evil Bunny

    Reversing polarity on a battery?

    A colleague of mine (who I trust is telling me the truth) just told me that he has seen a completely dead battery (a car battery) recharged so that the polarity was reversed from its original configuration. I'm not well versed on the inner workings of a battery, but I thought the chemistry...
  6. N

    Aromatic Substitution Polarity

    I have just been trying to teach myself about the effect of activating and deactivating groups on electrophilic substitution. However, I am a bit confused as to why the amine group in procaine (anesthetic) is in the para position, when the aromatic ring is attached to a deactivating ester. What...
  7. A

    Current transformer polarity and power flow

    Hello i need to know , does the polarity of the current transformer affects the power measurements in AC systems, and if it does , how it affects the power measurements knowing that in measuring power we use the RMS values anybody have any idea about this ?? that's to say , if you have...
  8. K

    List the solids in order of increasing polarity.

    Homework Statement List the solids in order of increasing polarity. NaCl,C10H8, C6H5COOH, NH2CONH2. Homework Equations N/A The Attempt at a Solution C10H8, C6H5COOH, NH2CONH2, NaCl. My rationale is that the longer the carbon skeleton the least polar.
  9. A

    2-wire dc polarity reversing signal

    Hi Does anyone know what a 2-wire dc polarity reversing voltage signal is? I have never heard of this type of signal before. I have gone insane trying to google it but to no avail. Any sort of help will be much appreciated.
  10. S

    Reverse polarity in torque motor

    I need to control a torque motor using variable voltage. I also need to have it rotate in reverse. Basically what I need it to do is start at +24VDC at one end, hit 0VDC in the middle, then finish up at -24VDC. Is there a potentiometer that can reverse polarity at the halfway point or do I...
  11. S

    What does reverse polarity in a DNA molecule mean?

    Ok I can see the 5 end is negative, is the 3 end positive due to OH. So in other strand this goes other way round. Is this what they mean when they say there is reverse polarity in a DNA molecule. Thanks!
  12. S

    Determining the polarity of mutually inducted voltages using the dot convention

    Homework Statement Determine the polarity of the induced voltages in L1 and L2. [PLAIN]http://img406.imageshack.us/img406/730/31761140.jpg According to the dot convention rule, when current enters the dotted terminal of a coil,the polarity of the voltage it induces in the other coil is...
  13. P

    What is transformer polarity and how does it affect the output?

    Hey guys, i cannot make heads or tails of the concept of "Transformer Polarity". Tried looking for the material on the web but still couldn't get it. So, please help me out with dot polarity! Thanks
  14. S

    Weak & Strong Magnet attract each other no matter what polarity

    Recently while working with electromagnet , we noticed one thing. I we bring strong magnet near very weak PM or electromagnet, It will attract the weak one whatever is the polarity of magnets. we increased power to electromagnet then it was giving repulsion. I did't understand this...
  15. K

    Preserving Magnetic Polarity in a Revolving Reference Frame

    ***not homework for any class*** Title: "Preserving Magnetic Polarity in a Revolving Reference Frame" Problem: How can a revolving reference frame (assuming an uncharged observer with negligible mass) observe the same polarity for a magnet in the case where the rotational speed is great enough...
  16. K

    Circuit for polarity detection

    Can anyone suggest to me a simple circuit constructed using digital gates for polarity detection? The circuit should be able to detect positive, negative as well as zero polarity. I need to check the polarity of a dc motor which is controlled by a bidirectional converter. The bidirectional...
  17. F

    Which is More Polar: Ethyl Acetate or Nitrobutane?

    i was wondering the polarity of ethyl acetate and nitrobutane, which one is more polar? As i face this question in test(liquid chromatography using normal phase and reverse phase) Asking for the elution order, i am not sure which one is more polar? Can anyone answer my question? Also, if i...
  18. A

    Transistor ac output voltage polarity

    greetings, when a transistor in common emitter configuration is given a ac signal with base current,the amplified output form from collector of it gives inverted polarity of the input voltage or the output graph of voltage versus time gets inverted of input graph of voltage versus time.how is...
  19. M

    What does polarity of voltage mean?

    Homework Statement For part of my physics lab, I used an oscilloscope and approached a pickup coil with a bar magnet... and I saw that the line on the oscilloscope moved down when I removed the N pole of the magnet away from the coil, and the line moved up when I removed the S pole from the...
  20. D

    Interested in the whole earth magnetic polarity swap thing

    Hello, I am just very interested in the whole Earth magnetic polarity swap thing. I was informed by my Geography teacher as far back as 2001 about it, he said that the Earth was due for a magnetic polarity swap pretty soon. I watched a program on Saturday about it. In the program they stated...
  21. C

    TLC plate in regards to polarity

    I used a "normal" phase alumina TLC plate with 20% (v/v) dichloromethane/hexanes. I found the substance that traveled the furthest to be the most polar one (though the substance is not very polar, xanthohyll). Why would this be? I was under the impression that since the plate is polar and a...
  22. L

    Have electromagnetic waves any polarity?

    Hi, My doubt is how can the EM waves interact with an electron, i.e., electron is a particle with negative charge.. have EM waves any charge to attract or to repulse an electron ? :confused: An example is the microwaves oven when waves interact with water molecules. Thanks :smile:
  23. H

    How to determine Polarity of transistors in a circuit?

    Hi all, In following image thare are Positive(+) and Negative(-) signs on above and under VEB and VCB What's meaning of these signs?are they polarity of transistor? why beside connection to ground is a negative sign? thanks in advance.
  24. F

    Additive and Subtractive Polarity

    In the case of step-down transformers: The polarity between the primary and secondary transformer is subtracting when supplying test voltage to the primary transformer in the case where the H1 is matching the X1. Now if the polarity markings are wired but switched on the transformers to...
  25. C

    PM generator direction vs. polarity

    Hi, I have a 24v 250w PM DC motor that is being used generate electricity. Problem is that the way it is installed, it can be turned in either direction which of course gives me a polarity problem. I'm sure there is a simple solution, but could someone tell how I maintain a constant...
  26. F

    Chemistry Solutions and Molecular Polarity

    How would you determine which layer is which without using the densities?
  27. J

    Chemistry Solutions and Molecular Polarity

    Q: When water and chloroform, CHCl3, are mixed, the two components separate into two distinct layers, each of which smells strongly of chloroform. Account for these observations in terms fo the polarity of the two substances involved. Describe how you could very quickly determine which of the...
  28. R

    Comparing Magnetic Attraction: Iron vs. Opposite Polarity

    Lets say I take the North pole of a magnet and place it 1 inch from a mass of iron with the same density and shape of the magnet, and somehow measure the force of attraction, I'll label that value "i". And then I take that same magnet and place it the same distance from another identical magnet...
  29. F

    Finding the polarity of fridge magnets

    Hi guys. Im reading on some magnetism and I thought, what is the polarity of a fridge magnet? Does anyone have any ideas on how I might find out what the polarity of a fridge magnet is, ie what the field direction is?
  30. J

    Dual halfwave rectifier polarity inverter

    Dear honored forum members. Thanks in advance for any information and help. The title of this post might not be technically correct, but it incompases the issues that I am working with. My goal is to charge a 48 volt batterypack from a 12 dc volt source. I need a rather high amperage...
  31. D

    What could cause a battery to read negative voltage and how common is it?

    This isn't an engineering question, but I don't know which forum is better suited to ask. I pulled two AA batteries out of my daughter's toy this morning after it had been left running all night. One of the batteries read 0.80 volts, and the other read -0.24 volts! That's right, one was...
  32. DaveC426913

    Capacitor Polarity: Which Edge is Negative?

    I'm an only somewhat-experienced electronics tinkerer. I'm working on a board from an older widescreen TV. It has these kinds of capacitors: I've looked everywhere online. Which edge is negative? The black(purple) or the grey?
  33. S

    Why do some capacitors have polarity?

    Really, after I became an electrical (control) engineer, until now i do not know why capacitors like Electrolytic and Tantalum Ones, have polarity. can anybody answer me please?
  34. M

    Collapsing fields and coil polarity, freewheel diode, .

    When a DC coil (relay) is denergized, shouldn't the collapsing field cause a current that would oppose the change in current? Wouldn't that induced current be in the same direction as when the coil was enegized? Not seeing how a freewheeling doide gets forward biased. If I apply Lenz Law...
  35. G

    Can You Safely Use a Center Tapped Transformer for a Dual Polarity Power Supply?

    I'm designing a set of voltage and current sensors for use with a solar system. I have developed all of the circuits, but it requires both positive and negative voltage supplies. I want to use the classic design using a center tapped transformer with two regulators. But I'm not sure what will...
  36. R

    Dual polarity power supply circuit question

    I'm having trouble with the power supply portion of an opamp circuit I'm working on. The supply is +/- 5 Volt using 7805/7905's. Half wave rectifiers provide the unregulated input with 1000uF input caps and 100uF output caps. AC is supplied by a 13VAC 'wall wart' with no center ground tap...
  37. N

    Confused about Polarity of Induced EMF (Lenz Law)

    Hello, I am currently working through Faraday's Law and I am confused when my two textbooks don't explain how they set the polarity of V_{emf}, particularly when they say "the sign convention for V_{emf} is arbitrary in that it depends on the assumed direction for dS". How is the polarity...
  38. A

    Invert polarity of output DC voltage

    I'm building a power supply which is shown below : http://img397.imageshack.us/img397/3736/80123303ma0.jpg The tricky part is that i want a dual polarity PSU so i duplicate the circuit but this time i want to invert the output DC voltage as to be a negative one...what is the simplest...
  39. R

    Polarity of Wire: North/South Poles?

    Homework Statement There is a straight current carrying wire. A magnetic field is produced round the wire. Will north pole and south pole be developed?
  40. S

    Electromagnets and switching polarity?

    [SOLVED] Electromagnets and switching polarity? Hi people, I am relatively new to the forums and am experimenting with a new toy I want to try to make. I am stuck on the subject of changing polarity quickly in an electromagnetic coil and automatically. Let me explain. I have two rubber...
  41. J

    Find Currents & Vab with Reversed Polarity Battery in Circuit

    Homework Statement The 10.00V battery in the figure is removed from the circuit and reinserted with the opposite polarity, so that its positive terminal is now next to point a. The rest of the circuit is shown in the figure. Find a, the current in each branch and b, the potential difference...
  42. M

    DC Control systems and polarity

    Control and protection electrical circuits are one of the important portions of electrical systems designed and shown by standard symbols. Usually the circuit is supplied by positive and negative polarity of one battery. In almost electrical circuit diagram sheets we can see a positive line of...
  43. S

    Polarity of Aromatic Compounds

    Homework Statement I just wanted to check which is more polar: methyl benzoate or methyl m-nitrobenzoate. Homework Equations See below. The Attempt at a Solution The nitrobenzoate is more polar because it has more electronegative atoms bonded to a carbon, so there is a greater...
  44. F

    Which has higher polarity, sec-butyl chloride or tert-butyl chloride?

    Homework Statement I just need to know which of the two, sec-butyl chloride or tert-butyl chloride, has the higher polarity. Homework Equations I know that better electron withdrawing groups have higher polarity. The Attempt at a Solution I am learning towards sec-butyl having a...
  45. S

    Gravitational polarity, called antigravity

    Hello I would like to speak to you about the gravitational polarity, planet by planet. An old theory of India tells that the Moon was ejected from red spot of Jupiter… This theory is could all change. The author Jules Verne really knew that... It would be interesting to test the...
  46. S

    Testing AC Polarity with LED: Tip & Ring

    We routinely test "continuity" in our phone lines by holding a red/green LED to our "tip" (hot) and "ring" (cold) which lights up bright red if all is well with the AC signal. A bridge rectifier added to the mix let's the "green" shine; reversing the LED wires on + and - will make the...
  47. C

    Polarity and distribution coefficient

    I need to determine polarity of 3 compounds in order to intuit the relationship between their distribution coefficients in Ch2Cl2 and H20. The three compounds are benzoic acid (with a carboxyl group on a benzene ring), succinic acid (a straight chain with 2 terminal carboxyl groups), and...
  48. S

    Where Do HCl and NaOH Rank in Polarity Among Organic Compounds?

    Rank these compounds from least to most polar. These are the following organic compounds that I ranked in increasing polarity: hexane (nonpolar) methylene chloride ethyl alcohol methyl alcohol water (polar) Now there are two inorganic compounds that I don't know how to place in...
  49. A

    Reversing the polarity of capacitor?

    Hi everyone, I don't know if this could be understood here but I don't have any way of putting the diagram here so I'll try my best to illustrate it as clear as possible I hope it's understandable and please bear with me! If I connect to capacitors, one 1uF and the other 2uF in parallel...
  50. F

    Engineering Basic Circuit Analysis - confused about self polarity

    This question is bugging me, and I think I need to get it answered before I move on to working on the "harder" problems. I hate being stumped by the little stuff like this. Anywas, I'm including the question that I have as an attachment, it will be easier for all. Thank you!
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