What is Voltage drop: Definition and 201 Discussions

Voltage drop is the decrease of electrical potential along the path of a current flowing in an electrical circuit. Voltage drops in the internal resistance of the source, across conductors, across contacts, and across connectors are undesirable because some of the energy supplied is dissipated. The voltage drop across the electrical load is proportional to the power available to be converted in that load to some other useful form of energy.
For example, an electric space heater may have a resistance of ten ohms, and the wires that supply it may have a resistance of 0.2 ohms, about 2% of the total circuit resistance. This means that approximately 2% of the supplied voltage is lost in the wire itself. An excessive voltage drop may result in the unsatisfactory performance of a space heater and overheating of the wires and connections.
National and local electrical codes may set guidelines for the maximum voltage drop allowed in electrical wiring to ensure efficiency of distribution and proper operation of electrical equipment. The maximum permitted voltage drop varies from one country to another. In electronic design and power transmission, various techniques are employed to compensate for the effect of voltage drop on long circuits or where voltage levels must be accurately maintained. The simplest way to reduce voltage drop is to increase the diameter of the conductor between the source and the load, which lowers the overall resistance. In power distribution systems, a given amount of power can be transmitted with less voltage drop if a higher voltage is used. More sophisticated techniques use active elements to compensate for excessive voltage drop.

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  1. D

    B Found a circuit where current is zero across an ohmic device (dV>0)

    I know that a voltage difference doesn't necessarily imply current flow, but all the explanations I seem to find of that either say that that happens because the resistance is infinite, or there is nothing connecting the two points in question (the two are basically the same thing, as I...
  2. A

    How to figure the voltage drop at different points along a circuit?

    I'm trying to determine how to measure mathematically the voltage drop at various points along a circuit with loads at different points along the way. Let's assume all loads on 100% when the circuit is on. For a basic formula I use (for single phase): 2 * K-Value (12.9 Cu) * Amps *...
  3. Muhammad Usman

    I Physics domain analysis of Voltage drop in series resistor

    Hi all, I apologize if its a very basic question but this is related to my quest to know the things deeply. And it is not homework help at all, it is just a general question. The main question or objective to ask this question is to understand what is actually happening in a circuit with one...
  4. Lay1

    Understanding Voltage Drop in a Circuit

    Here is the figure mentioned above. My thinking is that for maximum current, resistance must be minimum. Thus, R1 is not considered which means the voltage drop of R2 is 10V. So, R2 is 1kohm. For minimum, I=2mA, so R1+R2=5kohm, since R2 is 1kohm, R1 must be 4kohm. This is how I deduce. However...
  5. livio

    Estimates of voltage drop with distance in weak electric field

    If I resolve the equation in 0, imposing a voltage value of 5 mV, it gives a non real solution, therefore I cannot resolve it for R=1 because I do not know which voltage value to impose. I am sure this is simpler than I am putting it :) thanks for any advice!
  6. J

    Engineering Voltage drop across drain-source for stacked MOSFETs

    Here's the circuut: Vtn is 0.7 V. So Vs1 (wrt ground) cannot be more than 4.3 V else M1 won't turn on. Likewise Vs2 and Vs3 (wrt ground) cannot be more than 4.3 V else M2 won't turn on. So Vs3 = 4.3 V. Even voltage across final resistance is 4.3 V Assume there's no drop across Mosfet. But I'm...
  7. S

    Finding the voltage drop along a tapered wire

    The actual homework question is about finding the voltage of a tapered wire, one where the two ends are different sizes (1cm and 2cm in this case). I've been searching for an equation to do this simply by just plugging in the values I have and I came across this. Where is resistivity, h is...
  8. altruan23

    Simple voltage divider -- why does this work?

    Summary:: don't understand how can we use a voltage that has been already dropped. I don't understand the voltage divider. So R1 and R2 are the same. I have 10 V in beginning, then 5V drop across R1 and then i have 5V drop across R2. But how can I use the 5V if they already dropped at R2? If...
  9. S

    Minimizing the voltage drop across a capacitor (solution shown)

    The following is the question and the solution to the question. I understand the solution to the part where you find the Ceq and derive Qeq from the equation Q = Ceq*V. However, I do not understand where V1 = V0-V2 come from. When calculating the minimum voltage, how do you come up with the...
  10. PhysicsTest

    Voltage drop across a resistor

    Really very elementary one, if i refer the circuit below For the source in the direction of current the polarity is -Ve to +Ve that is understood which is conventional current, but in the case of resistance in the direction of current the voltage V_R polarity is -Ve to +Ve. Why for resistance...
  11. AdrianRodz1

    Voltage drop in a PCB power plane

    I'm trying to maintain a spec requirement of less than 3% drop from farthest pin to closest pin from source. I'used the entire layer for copper but my oart does not require such a large pour accept to handle high current. So I'm considering there's a trade off that should meet inthe middle of...
  12. Tryhard314

    Voltage drop across a capacitor and resistor in series

    In this circuit a battery,Capacitor,and a resistance are in series. For simplicity assume that there is a +4V in the positive terminal of the battery and -4V in the negative one and let A be the capacitor plate connected to the positive terminal and B the capacitor plate connected to the...
  13. M

    Engineering Calculating Voltage Drop Across Non-Ideal Diodes

    So I have this circuit up above and I need to find the voltages across each of the diodes. The only info given is that they are identical silicon diodes at T = 300K. My first thought was that since the diodes are opposite, D2 would be in reverse bias and would act as an open. However, I realized...
  14. L

    An alternative and odd view of Voltage Drop

    I was going over some fundamentals with my son and I was trying to explain 'voltage drop' - To which appears to be some confusion on the net with respect to terminology. Many people are confusing 'voltage applied' and 'voltage dropped'. First I will explain what I taught - Let us look at the...
  15. Bheshaj

    Voltage drop: What do we mean when we say that voltage drops across a resistor?

    What do we mean when we say that voltage drops across a resistor?and what does it mean when we say that a point is at lower potential as compared to some other point?Can we say that potential is potential energy per unit charge?
  16. german_cargo

    Replacing a remote with a switch -- voltage drop problems :(

    I have a linear actuator that raises and lowers my snow plow blade and the wireless remote stopped working. Rather than order a new one for $200, I decided to splice into the wiring and put a momentary switch in my truck. I didn't like the remote anyways. I grabbed some wire and wired up a...
  17. N

    Why is there a voltage drop in a metal with no electric field present?

    Metals are highly effective at screening electric fields. If we place two contacts reasonably far away from each other on a piece of metal and apply a voltage bias, the charge carriers in the section that is far enough from both the contacts should be unaffected by the electric field. Why then...
  18. Kevin J

    How do you calculate voltage drop across neutral and ground?

    In our practical world, the voltage between the neutral wire and the ground is not exactly 0V, and there's some small current passing through the wire connecting the neutral wire to the ground, how do you mathematically calculate this voltage drop?
  19. E

    Voltage drop in the internal resistance of a voltage source

    In this circuit,first there will be voltage drop in the internal resistance of the voltage source.Mostly,the voltage source is assumed ideal in circuits,however,here a practical voltage source is assumed. So,there will be voltage drop in the internal resistance of the voltage source which will...
  20. HastiM

    Electric field from voltage drop

    Homework Statement Calculate the electric field given by a voltage drop of 1 V across an insulator with thickness 20 nm. 2. The attempt at a solution I am not sure which formula to use in order to obtain the electric field. I think one should use the formula E=U/d, where E denotes the...
  21. P

    Voltage drop conceptual questions

    I'm having trouble understanding how voltage drops. My understanding of voltage is a difference in potential, with potential being how much work is necessary to move a test charge to a specific orientation. So, if we have a circuit with say, a 12V battery and a 1 ohm resistor, and I had a +1...
  22. F

    What causes a voltage drop over a resistor?

    Why is the electrical potential greater before it passes through a resistor than after?
  23. A

    What Formulas Help Calculate Voltage Drop with Multiple Resistors in Series?

    So I have two formulas for calculating voltage drop. The first is: Vdrop = Vin * R1 / ( R1 + R2...). This let's me calculate the voltage drop on the first resistor in a series of 2 resistors. You can also extend this to more resistors in series just by summing all the resistors. However, I do...
  24. rocky4920

    FInding current in parallel and series circuits

    Homework Statement a. What is the net resistance in the circuit? b. What is the current through the 4 Ω resistor? c. What is the voltage drop across the 3 Ω resistor? Homework Equations R12 = R1 +R2 R34 =R3 + R4 1/Rt = 1/R12 + 1/R34 I3=I4 The Attempt at a Solution a) R12 = 2+ 3...
  25. T

    Why is there no voltage drop through this resistor?

    I have wired in series: + of 9V battery --- + of 1000 uF capacitor --- 660 Ohm resistor --- + of a green LED --- - of the 9V battery. Remark: the 9V battery is a bit depleted 7.8 V unconnected. Voltage drop across the capactor is 6.5V, across the LED is 1.5V but 0V across the resistor. Why...
  26. F

    Can the Voltage Drop PTC Thermistor Homework Statement be Solved?

    Homework Statement Homework Equations I am not sure exactly what this question is asking for, especially in regards to the voltage drop. How would the graph of voltage drop vs Rmax-Rmin be any different to what is already provided? The Attempt at a Solution
  27. N

    Using Ideal and Constant Voltage Drop Models

    Homework Statement I am practicing diode circuit analysis for an ideal diode model and constant voltage drop model.I have an initial circuit shown here: Which I then redraw to look like this: I want to make sure my process in redrawing this was correct. When I attempt to get current through...
  28. T

    How does increasing the source voltage affect voltage drop and load voltage?

    Does when why increase source voltage tu compensate losses why also increase voltage drop?. For example why increase current (reduce load resistance) and as side affect why increase voltage drop and then why increase source voltage tu counterbalance losses does also when why increase voltage...
  29. J

    Calculate voltage drop across the inductor

    Homework Statement An inductor of negligible resistance and an inductance of 0.2 H is connected in series with a 330 Ω resistor to a 12V d.c. supply. Determine: (b) the voltage drop across the inductor after two time constants(c) the voltage drop across the resistor after three time...
  30. W

    Voltage drop calculation for radial supply system

    Voltdrop calculations are made as shown below. Total loadLine currentI=1.5/−60∘⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯+2.3/−18∘⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ =(0.75−j1.3)+(2.19−j0.71) <<< (How to get to these numbers only from above??) =(2.94−j2.01 )=3.56/−34.4∘⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯MVA
  31. S

    Voltage drop and current through each resistor

    Homework Statement Determine the voltage drop and current through each resistor. *This is just my sketch of the problem since I couldn't take a clear picture of it. Homework Equations Ohm's law V= IR Parallel total resistance Req=1/R1+1/R2+1/R3+... Series total resistance Req=R1+R2+R3+...
  32. D

    DC motors in parallel causing voltage drop

    Hey PF, first time here, I have a problem I can't seem to solve! Any help is appreciated. I am using some DC motors with peristaltic pump heads to pump water (picture). I was having issues so I've broken my circuit down to the bare basics: 1) 12V regulated power supply 2) 12V motor 3)...
  33. Biker

    How does the voltage drop in a capacitor happen?

    Where does the voltage drop of a capacitor happen? My answer would be that It produces an electric field the opposes the field of the battery along the wires. So it is continuous lose to the capacitor which stores this energy in it. Another question related to this, When a positive charge hits...
  34. O

    Voltage drop across connecting wires?

    Homework Statement Suppose you want to run some apparatus that is 95 m from an electric outlet. Each of the wires connecting your apparatus to the 120 V source has a resistance per unit length of 0.0065 Ω/m. If your apparatus draws 2.9 A, what will be the voltage drop across the connecting...
  35. RoboNerd

    Figuring out how to approach capacitor problem

    Homework Statement Homework Equations C = q / voltage The Attempt at a Solution OK. [/B] By Kirchoff's Voltage Law, we have: EMF - ( q / Capacitance)x - (q/Capacitance)y = 0 Now. I know that having the dielectric increases the capacitance of X, so the voltage drop across it is smaller...
  36. G

    How can voltage drop be zero if E-field isn't?

    Hi. I learned that in an ideal conductor in a circuit, the voltage drop is zero. But how does this agree with the basic definition of voltage $$U_{AB}=\int_A^B \vec{E}\cdot d\vec{s}\enspace ?$$ The electric field inside a conductor only vanishes in static conditions, but in an electric circuit...
  37. G

    The true meaning of voltage drop

    In CE amplifiers with negative feedback I can't understand what it means that the emitter becomes more positive (when hfe increases and VE increases with it). Does it mean that there is less negative charge after the emitter resistor (going from ground to Vcc) and the emitter feels some positive...
  38. T

    Is voltage drop different in parallel circuits?

    https://puu.sh/qzv6o/5abc45494b.png I was under the impression that voltage drop was the same in parallel which would make it the power supply, but apparently not? Any insight would help. I know this isn't a hard a question, I'm just horrible at physics.
  39. G

    How Does Voltage Affect Diode Current Flow?

    I want to make something clear. Most diodes have in their datasheet some current for a given treshold voltage. For example a led will pass 20mA current when 4volts are applied to it. Or a zener diode's minimum turn on current is 10mA when 5,6 volts are applied across it. Does this mean this...
  40. J

    Is the Formula for Voltage Drop Across Capacitor Opposite of Resistor?

    Homework Statement I'm trying to calculate the voltage drop across a 60uF and a 30uF capacitor in series, powered by 60V. Is the formula for voltage drop across capacitor opposite of the formula for resistor, where resistor is R1=R1/(R1+R2) while capacitor is C1=C2/(C1+C2)? Homework...
  41. A

    Why does the voltage drop across a diode change with increasing current?

    Homework Statement I have recently performed an experiment where the voltage drop and current through a diode were measured. I am wondering why the voltage drop across the diode changes. Theoretically, the voltage drop should stay the same as there is a certain amount of energy required to get...
  42. John Pang

    Voltage drop in an electric circuits

    I don't understand why the voltage drops only when the charges in an electric circuitnpass through resistors or electric devices, but don't drop as charges move through the wire. As charges move through the wire due to electric potential differences, from a high potential to a low potential...
  43. M

    MHB Tutoring for voltage, charge, terminal voltage drop , temperature coefficient.

    I have several problems regarding this/these topics. Is anyone available to tutor me right now? Thank you.
  44. F

    Voltage drop across voltage divider

    Homework Statement A voltage divider with two resistors R1 and R2 is given. The output is connected to a transistor so VB is always equal to the base emitter voltage=0.7v. Homework Equations How can i explain physicaly (wath happens to the electron flow and such) why when R1 is verry high, VB...
  45. AstroJMT42

    Voltage drop and transformer improvement

    Homework Statement Power station produces AC power at 2.5Mw, I = 100A. Transferred along 100km line with a resistance of 50 ohms to a factory. Calculate power lost and % efficiency Homework Equations P=VI P = I2R The Attempt at a Solution Initial power at the station is 2.5x106 . Using I2R...
  46. terryds

    Voltage drop between two points

    Homework Statement The question is: What's the voltage drop between point A and B ?? (Suppose that E2 > E1)2. The attempt at a solution First, I need to solve the current flowing in this circuit, which can be done using KVL. The current flowing is ##\frac{E_2-E_1}{R_1+R_2+R_3+R_4}## (which...
  47. G

    Do motors have some voltage drop across them

    Homework Statement Homework Equations Hello, i have been thinking, what couses a dc motor to have let's say 6volts drop across him. I was thinking that since it is just a coil it should have a verry little voltage drop, but afted testing on breadboard i figured out that it have near 6 volts...
  48. T

    Voltage drop calculations for CCVT's and Current TF's?

    I have not found a straightforward explanation on how to perform voltage drop calculations for cables used for instrumentations purposes. Suppose you have Current Transformer (CT) and Potential Transformer (PT) connections coming into a relay (IE SEL421). If we have a cable that runs from the...
  49. dep0

    What is the Voltage Drop across a dependent current source?

    Hello, I want to calculate the Thevenin/Norton equivalent of a circuit with a dependent current source. I tried to analyse the circuit using loop equations but i don't know how to calculate the voltage drop across the current source. Any help would be appreciated.
  50. C

    Voltage Drop Question: Calculate w/o I

    i have a 24 volt buss in a machine and i need to connect an lvdt sensor to the plc i show a 1.5k resistor that is .5 watts on the lvdt. what need to find out is the voltage drop at the resistor. i formula asks for I but I but i don't have I so what might the votage drop be. answer or formula...