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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705 views

Calculated resistance of an LED [duplicate]

I am working on some circuit lab homework this week and am a bit stumped by something I just can't seem to find anywhere in my Circuit Analysis I book. The lab has me construct the following circuit ...
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184 views

resistors misconception - is current-limiting effect circuit-wide?

Resistors are used to drop current Amp and Voltage, following Ohm's law. I can't understand some of their applications: we use them cause we sometimes want to drop the voltage a little in a specific ...
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Determining Resistor for Heating Element

I am attempting to run a Molybdenum heat coil. The best I can tell it is 0.3-0.4 ohms per rack and I would like to run say two racks at 230V at 3.9KW (so it doesn't trip my 230V 20 amp breaker). Does ...
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119 views

Equations for voltage/current through a transistor

Given the following circuit: I can figure out the current through the 'bottom wire' by doing: ...
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74 views

What is a Current Source? [duplicate]

In EveryCircuit, they have a component called a "Current Source". For example, here is a circuit I've created with a 2A current source: Is there a such thing as a 'current source' in the real world, ...
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59 views

current drawn by led increase with more leds you put in parallel??against V=IR?

current drawn by led increase with more leds you put which i saw in a video about thyristor ,but more leds means more resistance which means lesser current which is not true as per the video(https://...
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362 views

UJT Negative Resistance and Ohm's Law

A Unijunction Transistor has a negative resistance region where voltage drops with an increase in current. This was explained to me as a situation where "Ohm's Law is broken". This doesn't sit well ...
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120 views

Add a LED and a resistor to a working circuit

We found, with my 6 y.o. kid, a 9V battery and an old CPU fan power supply fan, and we were happy to see the following circuit 1. working. Then he asked: "Can we add a switch and a LED?" For sure we ...
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152 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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125 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 ...
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1k views

Resistors for transistor led circuit

Im new to electronics and have problems with calculating the resistors needed for driving an IR LED with an transistor. My VDD is 3.3V, the LED needs 1.3V and I want to drive it close to 20mA, so I ...
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98 views

Why can Ohm's law be used in a linear circuit with multiple equivalent resistors without being given current?

I'm exploring voltage dividers and am puzzled by the conclusion made by the YouTuber in this video: "If you apply Ohm's law, you find that 1 V spread across two equal-value resistors gives you 0.5 V ...
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883 views

brief explanation of Ohm's law

How can I calculate ideal values of current for both short and open circuits by using Ohm's law. Further more usually said that it is not advisable to connect DC batteries of different voltages in ...
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853 views

How can this circuit read a value for amps at 0 volts

I made a simple circuit using this: It can tell you the voltage and current along a wire if you mouse over it. The wire down the bottom reads 4.55mA and 0V (the little yellow dots actually move to ...
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443 views

Parallel circuit and Ohms law

Theoretical questions with ideal components.(R2 is 10 Ohm) 1) parallel circuit. R1 and ammeter, If I have a parallel circuit of 2 resistances, both zero Ohm, the current would split to 2 and each ...
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144 views

Regarding the design of a basic voltage divider

I've just entered the fabulous world of circuitry and was wondering about the design of voltage dividers. I understand their function and formula quit well, but was wondering about the actual ...
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3answers
230 views

how does ohms law apply in power system

It appears that either all the people over the internet have either not thought about this question or that I am mistaken in my thought somewhere: Confusion appears when I try to apply ohms law to ...
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1answer
3k views

Connecting a parallel port to an Arduino

This is my first Arduino project and while I remember a (tiny) bit of electronics from school I'm struggling to get this working - in fact I've just fried a parallel port PCI card! I'm looking to ...
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1k views

basic math question about voltage, ohms, resistance

total n00b here. After working on several projects by copy & paste from other people's schematics and code, I'm finally digging in and learning some of the math to know what I'm doing. If I have ...
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2answers
85 views

Equations for a simplified transistor circuit

In the following circuit: I would like to greatly, greatly simplify how the components work just to be able to make a dumbed-down version of the equations. Let's assume the forward-voltage of the LED ...
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1answer
51 views

Measuring Voltage drop across MOSFET 2N7000

My setup is 2.1V on the gate. A 330 Ohm load between Vdd and drain. And Source to ground. I stepped Vdd from 0V to 9V in small increments and measured the current through Vdd to ground. Got currents ...
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2answers
62 views

Is current pushed through the circuit or taken by the circuit?

I am not an electrical engineer so my concept about the practical side of ohm's law is very flimsy. What I am going to ask may sound childish but please try to explain as best as possible. When you ...
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169 views

Does voltage and current have an inverse relationship in DC power transmission?

Let's suppose that we want to transmit a 1kW via DC generator with the below voltage level. From this we can see that the relationship between the DC voltage and current is inversely proportional, P ...
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1answer
365 views

Problems with input leakage current in a microcontroller

I'm trying to build a system in which a microcontroller receives (through one of its input pins) a logic 1 if a switch is pressed and a logic 0 if it's not. For that purpose, I want to implement a ...
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409 views

Can you calculate internal resistance of battery by shorting it?

Can I measure the current of a battery by shorting the circuit and by ohms-law divide the voltage of the battery by the current measured to get internal resistance?
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76 views

What’s wrong with my resistance calculations?

I was trying to use ohms law, and there is something I don’t understand. There is a blender that uses 240v at 0.25 A. 240 / 0.25 = 960 ohms However, when I tested the appliance with a multimetre, it ...
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312 views

Resistance in Ohm's law

Hello everybody I have a question about resistance in Ohm's law, according to the formula "I = U/R" the less resistance you have, the more current you got and accordingly the more power you drain. So ...
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92 views

Using Nodal Analysis Method

Question: I had solved easier circuits problem using nodal analysis but this one it has supernodes on nodes 2 and 3 which I find it difficult solving. thus I need help as I am trying my very best to ...
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1answer
149 views

Why the resistors needs higher Ampers if the Total current is 4 Ampers?

I have a question about the circuit as shown up. My question is if the total current is 4 Amperes, why do the resistors need a higher current? Am I missing something? If that so, what it is?
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3k 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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71 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 ...
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1answer
212 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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568 views

Simple KVL Problem Not So Simple

We're only a week in to the first EE class here at Uni and I'm already stumped. I can build a power supply in my sleep but anything theory-related turns me upside down. Now, I've done KVL on the ...
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1answer
119 views

Power consumed by an LED in a simple circuit

I am in the very beginnings of studying circuits and am a little confused on calculated Power. If I have a 9V Battery, 4 x 10k Resistors and a single LED, how would I calculate the power consumed by ...
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973 views

If I put 12 volts across a 1 ohm resistor, will it pull 144 watts?

I would think putting 12 volts across a 1 ohm resistor would pull 12 amps of current, and since watts=volts*amps the resistor would be dissipating 144 watts of heat, all of this assuming the source ...
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404 views

Verification on Ohm's Law?

I'm building some Heated Motorcycle Grips and I think my calculations are off. Can anyone help me verify that for 10 feet of 20 gauge Nichrome 60 wire, I have the correct Ohms, Watts, and Amps for the ...
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218 views

arduino current

I want to start learning EE with Arduino so as a project I decided to build an Ohmmeter and measure a (specific) resistance that should be about 100 KΩ ±50KΩ. In order to probe for that resistance I ...
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1answer
495 views

How do I calculate voltage on a multi-powered DC circuit where all ends go to ground?

I'm writing software that will calculate the correct voltage on each component, given the state that the DC system is currently in (ex. what power sources are on, what relays are open, fuses popped, ...
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1answer
63 views

finding I(current)

I am learning about step response in RC and RL circuits and one of the problems i managed to redraw as the image above; however, when I am solving for i the answer is -5mA. I am just confused on why ...
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2answers
553 views

Best resistance for RED/BLUE 3 lead LED

I have a project where a PCB has been manufactured with an error, where a 3 lead BI color LED (red/blue) has a single resistor to limit the current for both colors. I can fix this by hacking apart the ...
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1answer
64 views

Proper resistor for simple circuit

I have a potentially stupid question, but I have no idea how to handle the problem. I want to use 9V battery with a diode that requires 5V. So I need a resistor. How do I find the resistance if (as ...
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1answer
33 views

Figure out the Resistance Value With Known Device Specs

I'm learning electronics and trying to find the right resistor value for my device: a Eachine Rotg01 Receiver. The specs ...
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2answers
35 views

Position of the voltage source with parallel resistors

In the following circuit I want to calculate the current flowing through the voltage source (node A) simulate this circuit – Schematic created using CircuitLab If I use the KCL I get \$I_A = ...
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1answer
286 views

Switching Power Supply - Type of MCB for Inrush Current

it's regarding this PSU from Mean Well: https://www.meanwell.com/Upload/PDF/LRS-350/LRS-350-SPEC.PDF It has a 60A inrush current. My lighting circuit (1.5mm2 wiring) is tied to this PSU supplying ...
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75 views

amps were lower on ohms law math than what I read with live at the equipment? [closed]

When using ohms law on a residential A/C unit I got 7.3, But when using the multimeter it dropped to 5.5. What can cause this?
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82 views

How do I calculate the resistor value for this circuit? Will this circuit allow buzzer to work?

I have a circuit that uses an LED and a simple buzzer. I've created a basic circuit (below) and used a speaker to represent the buzzer. I know two things about the buzzer : Rated Voltage: 12V; ...
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1answer
37 views

Help understanding amperage of DC motor and heat generation

I am diagnosing an issue in an automotive HVAC system and have been testing the blower motor. I would expect somewhere approximately 8A to 15A of current draw. I have test wired the motor with 14AWG ...
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1answer
122 views

SMPS Current Sense Resistor Selection

I am looking into using an SPV1040 boost converter to charge a battery from a solar cell. The chip includes inputs for a current sense resistor, which are described in one of ST's applications notes ...
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1answer
81 views

What is the current flowing through the resistor in this circuit?

I have to find the current flowing through the resistor connecting node a to d. I know it's a current divider problem, but I'm having a hard time finding the correct expression. I presume R5 is ...
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1answer
69 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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