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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57 views

The best way to wind copper wire around rod for lowest resistance

So I have wound 200m copper wire around a rod which gives me 180 Ω, previously I got only ~80 Ω. Both of them were randomly shuffled and the first attempt was on bigger in diameter rod. How to make ...
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Why is Voltage and Current inversely proportional with Power, but directly proportional with Resistance?

Ohm's Law gives the relationship of Voltage and Current as follows: V = P/I and V = I * R. In the first equation, Voltage and Current are inversely proportional. In the second equation, Voltage and ...
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4answers
13k views

Why does current change when adding in an LED?

In the following diagram: The current is 1 mA from: V = IR R = 1 / 1000 = 1 mA However, when I add in an LED with forward voltage 1V: Why does adding in the ...
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70 views

Solving simple parallel/series without Req

Given the following circuit with three resistors, R1=100Ω, R2=200Ω, R3=300Ω: To solve this using the \$R_{eq}\$ trick: ...
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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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55 views

Relation between diodes and laser diodes

I am currently studying Practical Electronics for Inventors, Fourth Edition, by Scherz and Monk. Chapter 2.5 Resistance, Resistivity, and Conductivity presents makes the following claim when ...
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1answer
276 views

What does the arrow going through the battery symbol represent?

I am currently studying Practical Electronics for Inventors, Fourth Edition, by Scherz and Monk. Chapter 2.5 Resistance, Resistivity, and Conductivity presents the following image (without description)...
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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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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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1answer
50 views

Short and Open Circuit Calculation

Suppose there is a ideal voltage source which can provide infinite power if that is needed in an ideal scenario. Now suppose a resister R is connected across it and the e.m.f is E. So by ohm's law the ...
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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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3answers
57 views

Current flowing in a short circuit with a voltage source

I want to calculate the current flowing in the node A of the following circuit: simulate this circuit – Schematic created using CircuitLab This can be approached in several ways. The tension ...
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118 views

Can V=IR be applied to a short circuit?

Because on a short the voltage goes down while the current goes up, and a resistance of the line would be nill and remain unchanged. Does the formula fail or am I misunderstanding something?
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Difficulties in KVL signs (RL circuit)

If we start from bottom left and rotate clockwise, then first we visit resistor negative terminal so I expect -Ri but the book says the below equation: So why ...
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3answers
103 views

Further understanding Ohms Law

I posted a question earlier that helped me to understand Ohm's Law and how power is lost to length of wire due to resistance. So my original example was a 15A, 10ft cable surge protector plugged into ...
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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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81 views

Fraction resistance and negative resistance

Is it possible that the resistance will be fraction or negative number and what's happened?
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2answers
75 views

Dependent current source Mesh Analysis challanging problem

\$I\$ \$2\$ gets different value by different equations , Using mesh analysis . Please explain why \$I\$ \$2\$ has two different values using mesh analysis . My approach : \$-12I1+2I2=0\$ \$-2I2+...
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82 views

How can a light bulb run on different voltages (USA and EU)?

There is a concept in EE I don't understand. In Europe we have a 230 V supply voltage and in the USA e.g. 120 V. Now the thing I don't understand, how can I use my charger( or a light bulb) in ...
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183 views

Maximum power/current for a battery?

I'm learning electronics and found this question below, which is exactly what I've been questioning myself. But there was no good answer there, so maybe someone here can help. Original question: ...
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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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2answers
88 views

calculating Power

I wanted to ask, if I have a electrical component with a power rating of let's say 5W does this mean it would dissapate 10W after 2 hours and 15 W after 3 hours?? or is it correct to say it dissapates ...
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128 views

9 Volt battery connected with no resistance but current is not 9 A?

As per Ohms law , V = IR OR I = V/ R So if I set R to 0 , then V should be equal to I ? However when I connect 9 Volt battery poles to each other with multimeter in between the reading says 0.2 A.
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104 views

Non-equal batteries discharge in parallel connection

My friend and I have an argument and I want to ask the community to say who is right and who is wrong in their beliefs, and explain it with formulas and laws (if possible). We have two different Li-...
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1answer
101 views

Where did I miscalculate ohms law in my experiment?

I thought I finally had a grasp on how ohm's law works but when I set up an actual experiment, the numbers don't match up. To keep a long story short, I converted a computer power supply into a lab ...
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6answers
188 views

Ohm's law confusion

I've been trying to learn electronics stuff from this video series on YouTube: https://youtu.be/m4jzgqZu-4s At 1:07 in the video above, a switch is closed, SO there is zero resistance across the ...
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How do ohm meters measure high resistances?

I'm sorry if this is a stupid question, but I'm an apprentice and this doesn't make sense to me. I'm given to understand that an ohm meter measures resistance by passing a small current through a ...
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How do batteries connected in parallel give more current than batteries connected in series?

Let's say we have three 1V batteries and we're connecting them to a 1Ω resistor. Connected in series, the voltage is 3V and since the resistance is 1Ω, that means that from Ohm's law, the current ...
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4answers
235 views

Understanding “Current Draw” in terms of “Ohm's Law”

I'm having trouble understanding Current Draw as it relates to Ohm's Law (V = IR). I have a power supply rated at 5V and 500mA. I'm trying to power a string of LED lights. According to my ...
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284 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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48 views

Circuit Analysis Involving DC Motors

When it comes to simple circuit analysis, there is millions of tutorials on how to analyze a resistor circuit, a RC circuit, or those involving LED the non-ohmic devices. However, I did not find a ...
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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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I dont know how to caculate initial current [duplicate]

simulate this circuit – Schematic created using CircuitLab I have a circuit of just a 240 ohm resistors and a 12 v battery. In the circuit the current after the resistors is 0.05. what is the ...
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How does a transformer increase voltage while decreasing the current?

Ohm's law states V=I*R. That means when we increase voltage we must also increase the current(I.) But transformer increases the current while decreasing the voltage or decreasing the current while ...
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2answers
167 views

How can I find the voltage across R4?

I am trying to find the voltage across R4 in the following circuit: It confuses me that there are 2 voltage sources. I am not sure how to approach it, so I tried this: First, I use Kirchoff's ...
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1answer
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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How current works

I apologize for the very basic question but I seem to be lacking some fundamental knowledge. I am using an infra red LED in a circuit and it seems like it is drawing around 15mA at 5v. I was told ...
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2answers
80 views

A basic question on Ohm’s law and the definition of voltage

1 Volt is defined as: when 1 Joule of work is expended in moving 1 Coulomb charge between two points. On the other hand the Ohm’s law states: V = I × R I draw a theoretical circuit below where ...
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4answers
137 views

How can Ohms law be used to calculate the resistor value for an LED when multiple voltage/current pairings give the same resistance?

Say I have a 9V supply, and I want to power an LED that requires 3V and 0.02A. From what I understand, I need to add a resistor that will drop 6V, and reduce the current to 0.02A, and I can calculate ...
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106 views

120 Watts and 7.2 Volts, how many Amps?

For a project I need to switch on a simple handheld vacuum cleaner with an Arduino. I am thinking of using a relay or mosfet. I opened the case and a 7.4 V 2200 mAh Li-Ion battery powers the motor, ...
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96 views

How to calculate current in voltage divider with load?

Say, I have this circuit (please ignore the zeros, and the diode should be some load that draws 10ua): So, \$V_{in}\$ be 12V. I would say that D1 gets \$\frac{R_2}{(R_2+R_1)}\cdot2V\$ as voltage. ...
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1answer
682 views

Does a semiconductor follow Ohm's law?

Ohm's law is valid for metals, but is it valid for semiconductors? Does it work there? I am not talking about a PN junction here. If I have a block of silicon and pass voltage across it, will I ...
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Resistance/Voltage relation in Rheostat?

According to "How Computers Work" (Tenth Edition) by Ron White, he features a graphic of a potentiometer with three terminals on the bottom with the one on the left being for current flowing in and ...
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1answer
1k views

How do I calculate expected output voltage of car audio amplifier with given conditions?

I have a 4-Channel Amplifier rated at 800 Watt RMS per channel @ 2 Ohm load. Channel 3 and 4 are preset to operate a subwoofer speaker while Ch 1 and 2 are set to operate mid-range speakers at ...
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5answers
187 views

Confusion about Ohm's law and electrical power (basics of electrical engineering)..?

I am studying electrical engineering, but I still have some doubts about Ohm's law and electrical power. According to Ohm's law: \$I=\dfrac{V}{R}\$ So that means voltage is proportional to current. ...
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2answers
108 views

Parallel circuit with LED on one path and resistor on the other

I'm a beginner to circuits. Unlike many other questions, my circuit involves a parallel circuit with a LED on one path but a resistor on the other, as shown in the picture. Q1: assuming the LED has ...
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2answers
61 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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2answers
306 views

How should I chose a resistor for a home-made electromagnet?

I have a magnetic wire and I want to use it to make an electromagnet. The electromagnet will be powered by a 5V, 2A power supply. How do I know what resistor should I use in series in order to avoid ...
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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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