Read about ohms law | 24 Discussions | Page 1

  1. M

    Two batteries and two resistors circuit - wrong possible answers ?

    It's ABCD question with answers attached. Problem is that, I don't think that neither of those are correct. From KVL the equation seems to be i = (E2-E1)/(2r1+2r2 + R). I've attached images of the circuit, answers, and my solution. Can someone please point me if I am wrong, and if yes, where's...
  2. Oannes

    Finding the Current Through a Resistor (Working With Parallel and Series)

    Here is the actual question. And here is my attempt at a solution In Summary I did the following Found the Equivalence Resistance to Be 5.9 ohms and the Current throughout the entire resistor to be 1.53 Amperes Worked backwards from my resistor simplifications. When the resistors were in...
  3. L

    How would I solve this Mixed Circuit?

    Homework Statement The following circuit is given, and all voltage, current, resistance and power must be found for each resistor. I have found the following information: Vsrc = ? Isrc = .5A Rsrc = ? Psrc = ? V1 = ? I1 = .5A R1 = ? P1 = ? V2 = 2.5V I2 = .25A R2 = 10 P2 = .625W V3 =...
  4. Lapse

    What is the Voltage on C1/C2 after the switch closes?

    Homework Statement Homework Equations Vf+(Vi-Vf)e-t/RC Tau = RC The Attempt at a Solution [/B] Normally, I would use the eq'n mentioned above to find Vr in an RC circuit. However, this second capacitor is throwing me off. Is there a new equation I should use? How do I think about this...
  5. P

    Potential difference across a resistor

    Homework Statement Two cells of same emf E and different internal resistance r1 and r2 are connected in series to an external resistance R.The value of R for which the potential difference across the first cell is zero is given by (A) R=r1/r2 (B)R=r1+r2 (C)R=r1-r2 (D)R=r1r2 Homework Equations...
  6. D

    Voltage in parallel V1=V2=V3

    Homework Statement I have to write about voltage within a parallel circuit and the formula for voltage in parallel is Vt=V1=V2=V3. But I was wondering if that's only the case if the resistors have the same resistance becasue I used resistors with different values Homework Equations V1=V2=V3...
  7. Tony Meloni

    Question about Full scale deflection

    Homework Statement hello, just came across this type of question for first time. A voltmeter with a range of 0-30volts is to be used to measure a 120 volt circuit. calculate the value of the resistor to be placed in series with the meter. the sensitivity of the meter is 1000 ohms per volt ...
  8. S

    I Lightbulb in series question

    Hi Two lightbulbs in series, one with 50W one with 100W which is brighter. I have two different solutions and can't see my error. Using PR=V^2 and I^2=P/V 50/√50R1=100/√100R2 with the same current and R2=2R1. Using PR=V^2 and the same voltage across both bulbs yields 50R1=100R2 or R1=2R2. Which...
  9. I

    Calculating Input Voltage of a Step Down Transformer

    Homework Statement A pair of power transmission lines each have 0.68-Ω resistance and carry 650 Amp. If the primary voltage of the 10:1 step-up transformer is 4.6 kV, calculate the input voltage of the step-down transformer at the other end. Homework Equations P=IV V=IR IpVp = IsVs The...
  10. G

    Is there microscopic version of general Ohm's law of V=IZ?

    Hello. Resistive Ohm's law is famously known as V = IR. We can derive its microscopic version as being followed. V = El, where E and l are, respectively, an electric field and a resistive load length over which a voltage drop V is developed. I = JS, J and S are a current density and a...
  11. I

    How to find Voltages and currents of the following circuit

    Homework Statement The circuit of the given problem is attached to this post (jpg file). All info is given in the photo. Problem: find VA, VB, IA. Homework Equations Ohms law KCL equations P = VI or V^2/R The Attempt at a Solution - First, I noted that VB = 9 - VA. - next, i set up a KCL...
  12. B

    KCL Problem with Dependant sources

    Homework Statement I'm trying to find the voltage drop V1 of the following circuit, assuming Vin=1v, and for the life of me can't seem to get the right answer. Homework Equations KCL, Ohm's law The Attempt at a Solution I basically tried to use KCL at the top node, Vin/2+2V1 = V1/3 +...
  13. Glurth

    Odd troubleshooting results: disobeys ohms law

    I have a DC powered pump, that has suddenly stopped working. During troubleshooting I came up with the following results, that I just cannot reconcile: Input wires, not connected to pump: 12v Input wires connected to pump: 0v Sounds like a short in the pump right? However, connecting the...
  14. anorlunda

    Insights Ohm's Law Mellow - Comments

    anorlunda submitted a new PF Insights post Ohm's Law Mellow Continue reading the Original PF Insights Post.
  15. D

    Ohm's law and using motor as generator

    hello i was wondering about how a dc motor would work as a generator and how the voltage and current would scale with ohms law. for example lets say i had a 350 watt motor thats 36 volts and generates 9.72 amps now lets say i use that motor as a generator but only generate 200 watts how would...
  16. R

    I Calculation confirmation needed -- energy stored in heated water

    Hi Guys I'm new the PF and hope I'm posting I the correct place, apologies to admin if not ;-). I'm working on a project at home and maths is not my strong suit. I have an equation that I need to complete and involves converting thermal heat capacity in water into electric power. From what I...
  17. J

    Please check my answers: Combined Circuit

    Homework Statement Homework Equations The Attempt at a Solution Vt=30V It=4.3A Rt=7Ω V1=12.9V V2=2.15V V3=2.15V V4=4.3V V5=12.9V VA=4.3V VB=4.3V I1=4.3A I2=2.15A I3=2.15A I4=2.15A I5=4.3A IA=2.15A IB=4.3A R1=3Ω R2=1Ω R3=1Ω R4=2Ω R5=3Ω RA=2Ω RB=1Ω Did I break down the problem...
  18. J

    Combined Circuit Problem

    Homework Statement Homework Equations IR=V series circuit Vt = V1 + V2 + V3... It = I1 = I2 = I3... Rt = R1 + R2 + R3... parallel circuit Vt = V1 = V2 = V3... It = I1 + I2 + I3... Rt = 1/R1 + 1/R2 + 1/R3... The Attempt at a Solution i honestly have no idea where to start. may someone pls...
  19. S

    Inductors and circuit problem

    Homework Statement In the following figure, R1= 3.1 Ω, R2= 4.9 Ω, L1= 0.155 H, L2= 0.2 H and the ideal battery has ε = 5.6 V. Just after switch S is closed, at what rate is the current in inductor 1 changing? Homework Equations { \varepsilon }_{ induced }\quad =\quad L\frac { di }{ dt } \\...
  20. H

    How do you read the ratings of a relay?

    Hey guys, hopefully this is the right subforum.. Anyways, I am wondering how to read the ratings of a relay. Here is what I am looking at: http://www.ebay.com/itm/5pcs-5V-T73-SRD-5VDC-SL-C-5Pin-10A-Relay-Module-Arduino-ARM-PIC-AVR-DSP-/161755474571?pt=LH_DefaultDomain_0&hash=item25a960aa8b...
  21. M

    Calculating Current.

    Homework Statement Homework Equations Current = Voltage / Resistance. The Attempt at a Solution I know this requires me using the formula Current = Voltage / Resistance, but I'm confused to which measurements I use. I think possibly I take 0.9 from 5 volts then do 4.1 / 10000?
  22. S

    Engineering Series/Parallel Resistor Circuits (Diagonal Resistor)

    Homework Statement http://i.gyazo.com/c6b73ca3a53b7d36bce59a0aa5009d27.png Homework Equations Kirchhoff's Current and Voltage Laws, Resistors in parallel and in Series. The Attempt at a Solution The main thing confusing me is the diagonal 6 Ohms, not too sure what it is parallel too and how...
  23. U

    Is Ohm's Law applicable for only DC or for both?

    Is ohm's law (V=IR) works for both AC and DC. PLz explain in details Also let me know which formula is right for power calculation for AC and DC circuits. (P=VI or P=VICos)
  24. marcophys

    HT 'low current' resistance fundamentals in Tungsten Welder - event horizon

    Does anybody understand the fundamentals of what is happening in this circuit? Tungsten welding info is all about high current..... but this is a low current scenario. AC input, CDI Coil generated 20Kv (estimated) suffers voltage drop over 100mm of tungsten rod. The larger the diameter...
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