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Questions tagged [ohms-law]

A well known relationship that describes the relationship between Voltage and current through a device's resistance expressed mathematically as V= IR. This formula says that voltage across the device is equal to the current through the device multiplied by the resistance.

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12k views

Does a generator produce voltage or current?

I know that this question might sound very stupid for +90% of you, but my brain doesn't really get the electricity generation. The thing that I don't understand is what does a generator produce, ...
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3answers
234 views

Why voltage is the same after placing a resistor?

simulate this circuit – Schematic created using CircuitLab Hi. I'm testing a very simple circuit with a multimeter. In Ohm's Law, a resistor should affect the voltage, but in my circuit it ...
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1answer
143 views

How many amperes without resistance?

For the below circuit according to Ohm's law the led will get 23mA. What happens if the resistance is removed? How many amperes will the LED get? My assumption is that the wire has some kind of ...
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2answers
648 views

Current Flow into MCU pin

If I have an MCU, e.g. ATTiny85, and I connect a 5V source to a pin on the ...
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2answers
2k views

Calculating current in a series circuit

Given the following circuit, it seems like we could use ohms law to conclude that current = voltage / resistance. With a source voltage of 3.3 and a resistance value of 220, current = 3.3 / 220 = .015 ...
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2answers
68 views

Finding the heat dissipation but calculations not going right?

I am trying to find the heat dissipation from a 20000 V 1 A filament which is on for 1 second. I just randomly came up with this to try to test my understanding of joules first law and ohms law with ...
12
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1answer
3k views

Powering a 5v relay from a 12v power supply

I have a relay which is rated for 5v. My power supply is 12v. I have measured the resistance across the coil as 400 ohm. If I place the relay in series with a resistor that is 560 ohm, would it ...
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2answers
117 views

Three series LEDs on 5 V?

I'm new to electronics and Arduino. I bought the Arduino starter pack and I did the first exercise: connect a LED and a resistor. But after I tried to connect more LEDs, and when I connect 3 LEDs ...
32
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7answers
7k views

Why don't we use low voltage Power Sources for high wattage applications?

Super nooby question involving Ohm's law, but this has been on mind this morning. Say I have a 60W device, and I want to power it. Usually this calls for a 120V source or something. However, why not ...
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5answers
254 views

How are voltage dividers useful? I can't seem to get enough current for them to be useful

I must be doing something wrong here, because when I make my simple voltage dividers and do the math, the most current I could draw through my voltage divider would be 33.3mA. Here are my factors: ...
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1answer
226 views

Reason for inconsistency with Ohm's Law, of current measurements in resistor connected to battery circuit?

simulate this circuit – Schematic created using CircuitLab Connecting various resistors to the same two batteries rated 1.5 V and 9 V as shown in schematic above returns unexpected results: ...
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4answers
259 views

Is current calculation in copper wire for AC simple or not?

I'm trying to learn electronics by myself, and I'm starting with simple current calculations. Let's assume we have a straight wire of length L connecting a source and a sink. I know the voltage (V), ...
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2answers
803 views

How does electrolytic capacitors work?

Basically I am interested about the polarity of an electrolytic capacitor.How is the polarity of an electrolytic capacitor is defined and what if I reverse the polarity in a simple circuit containing ...
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2answers
1k views

Convert 24 V to 20 mA (none is variable)

I have a PLC (take the "P" with a pinch of salt), it has some analogue inputs (4-20 mA) that I need to use to detect if 24 V is present or not. I can program the logic to say above X mA 24 V must be ...
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2answers
1k views

High voltage transmission, transformers and Ohm's law

I have difficulties with understanding high voltage transmission and transformers working process. Particularly with this expression: "the higher the transmission line voltage, the smaller the current"...
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2answers
48 views

Would lower current cause a battery to go flat slower?

So I understand the basics of ohm's law and batteries. The electrons move from the cathode to the anode via the circuit and when the anode and the cathode have the same amount of electrons they stop ...
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3answers
87 views

Struggling to understand series connections based on experiment

I'm having some issues understanding how series connections work based on an experiment I did at school. I took two lamps, and then connected them in series so the power initially goes to the first ...
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1answer
64 views

Understanding equilibrium equations

I initially asked this question on math.stackexchange.com, but nobody answer so I thought I could try to ask here, this at least to some degree related to electrical engineering. Please help me to ...
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2answers
74 views

Will the bright of the bulb increase or still the same in this simple circuit?

If Lamp2 is disconnected, What will happen to the brightness of the Lamp3? I think that the brightness will remain the same because Lamp2 is in parallel with the branch that contains Lamp3. Let's ...
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2answers
96 views

Help understanding circuit with diodes in it

I'm having trouble figuring out how this circuit works in the real world. I know theoretically the diodes should have a resistance of 0, 0 and infinite respectively, which makes the question quite ...
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1answer
302 views

12V DC LED and motor circuit - overheating

I'm trying to build a model lighthouse (don't ask). :-) Essentially I'm trying to have an über-bright LED with a motor rotating at 2rpm, both powered from the mains (120V AC). The problem I am ...
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1answer
72 views

Ohms law and a resistor

I've recently just learned from the Internet that a resistor reduce current. But when I measured the amps from the power supple to the resistor in series and then measured again from resistor to an ...
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3answers
99 views

Finding the voltage of a circuit composed of a series and parallel?

I was watching a youtube tutorial to understand calculations using ohm's law and I thought I had it down when I ran into this problem: I was asked to find the voltage at points A and B. I was also ...
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1answer
510 views

Mesh-Analysis, Ohm's Law & Passive Sign Convention

I am using Fundaments of Electric Circuits 5ed and I have a few questions about Passive Sign Convention with respect to Ohm's Law & PSC FYI passive sign current (PSC) is based on this diagram: ...
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1answer
289 views

Application of Ohm's law to a single resistor and to a series circuit

For any given resistor following Ohm's law say a carbon resistor, it's resistance is independent of the value of current and voltage. However, say we had a 5 ohm resistor in a circuit with a 10V ...
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0answers
88 views

Why would venting an engine create a negative amperage on a generator?

I'm writing simulation software for a civilian helicopter. The helicopter has two engines and two generators. Normally, we calculate the amperage reading of a generator through Ohms. I = W / V. ...
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5answers
909 views

Quick Question about ohms law and resistors

This may have been asked before, but I'm currently I'm an argument about whether or not passing 12v through a .1 ohm resistor would result in 120 amps due to Ohm's Law. (I=V/R) Providing that the ...
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1answer
835 views

Parallel circuit-find value of resistor [closed]

I have a parallel circuit with 7.5 ohms as total resistance,75 volts, with 2 resistors. R1=10ohms,R2 is unknown. How can I find the value of R2?
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1answer
2k views

What would be the effective resistance in this circuit?

How would one go about calculating the resistance between points A and B on the following circuit: This is for Higher Secondary level. The person who needs to solve this understands these basic rules:...
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1answer
78 views

Why is the resistance of the circuits input voltage not taken into account when calculating overall resistance of the circuit?

When calculating the resistance in a circuit, one uses Ohm's Law i.e. V = IR with resistors in the circuit. But why is the resistance of the inputs not taken into account? For example, if one has ...
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1answer
124 views

Induced voltage of an inductor with a hollow core: can it produce current? [closed]

Hello I'm trying to understand a concept here: if I have a coil wound around a tube, with liquid flowing through the tube, will the electrical flux generated by the coil be enough to perform ...
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3answers
127 views

Solving for current through a wire

This is a pretty simple question really and I'll feel embarrassed when I get the solution but its bugging me for now. The goal is to solve for I going from left to right. No values given for any of ...
0
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1answer
205 views

Algorithm for “short-circuit” current draw

Alrighty let's pretend that the circuit contains no resistance other than the battery internal resistance and the wire's resistance itself, Would this be a correct algorithm? (Using OHM'S law) ...
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1answer
190 views

Claulating the resistance for the IR Flame Photodiode sensor

Hi I wish to make a IR Flame sensor. I have made a schematic as below. But I could not determine the values for R(x) & Rpot(y). I have tried x = 10K, y=10K , x=1K , y=10K,etc (randomly). But I ...
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3answers
109 views

How does Power over Ethernet combine cores to send power over longer distances

Sorry if this is too n00b a question, I'm struggling to wrap my mind around basic EE terms for my project. In my application I run 20 watts over a single AWG-24 wire at 5 volts. This works fine if ...
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3answers
1k views

Can a battery produce more amperes as per Ohm's law?

Ohm's law says I = V/R. So let's say I take a 9V battery and attach 1Ω resistance across the terminals. So the current running across will be 9A. But the battery rating says only 500mAh. So are ...
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3answers
304 views

Is current/resistance a parabola? (For lack of a better word)

So it occurred to me today that is resistance is the load that draws current, but also the thing that limits it, wouldn't a graph of current to resistance increase, but then decrease?
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2answers
80 views

Why lights dim when the AC compressor switches on

If two points in circuit are not connected there is supposed to unlimited resistance between them. So when the compressor is added to circuit it is either very high resistance or very low. In either ...
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1answer
3k views

How to calculate the maximum cable length of fire detection loop

I have been tasked with writing a software to calculate the maximum cable length of the fire detection loop, I am not a electrical engineer myself and therefore I am struggling with some of the ...
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2answers
123 views

What is kU (V/V)

I have following task I know it's probably really simple (just simple Ohm's law), but I have no clue what kU is. Could anyone explain it to me in the simplest way possible.
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2answers
760 views

How to apply Ohm's Law correctly to a circuit?

Ohm's law continually confuses me in my attempts to use it. Right now I'm trying to supply a maximum of 800 mA by 1.5 V from a 5V source. Does that mean that I need a 1.875 Ohm resistor ...
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1answer
487 views

led lights resistor

I recently installed an H7 Led Headlight kit 12V/25W in place of a standard halogen 55w bulb. Lights are great, but they flash periodically during can-bus Cold/Warm checks to see if a bulb is out. I ...
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3answers
4k views

How did scientists deal with electronics' problems before Kirchhoff and Ohm's laws?

Both physicists developed really powerful laws which still nowadays rule the electronic behavior of circuits. These help us every day to solve problems, calculate circuit variables… but how did ...
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2answers
528 views

Volts for power supply, and ohms and watts for the resistor [duplicate]

I'm very new on this for this has never been taught in my school. I have ten 5mm blue LEDs. Each led has 3.4V and 30mA max current. The only thing I know is that I have 34V for my LEDs. The power ...
0
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1answer
858 views

How does an MCU pin detect a voltage?

If I have an MCU pin connected in between 2 resistors (a voltage divider) how does the MCU ...
2
votes
2answers
95 views

Calculating for current in a single transistor amplifier(almost common collector?)

I was given this circuit for a practice test during one of my classes, but we were never shown how to actually solve it. It's just been bugging me so I wanted to know how others solved for all the ...
0
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3answers
252 views

Why is the calculated current with P=VI and R=V/I not equal?

I'm just starting to learn electronics. I thought I'd start with a simple project of attaching a speaker to a Raspberry Pi (it supplies 3.3V). The speaker I've picked is an 8Ω 0.5W speaker. Now as I ...
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3answers
397 views

Sparkfun using 500Ω resistor on circuit with 9V battery and 2V/0.018A LED

A Sparkfun tutorial explaining voltage, current and resistance shows a simple circuit where a LED is powered by a DC source (9V battery). The LED is a red 2V/0.018A LED. The tutorial explains that ...
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2answers
218 views

Can anyone explain the ohm's law apply here?

What i am seeking is to explain why the relationship here is not V2/R2 instead it's given as (V1-V2)/R2
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1answer
10k views

How is open-circuit voltage calculated?

I'm pretty new to circuits and I only know basic rule from Ohm's law that U=I*R. I quite don't understand how was following formula for Ui created: Why are there only two resistances in numerator? ...