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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1answer
60 views

How do you set amperage in a simple circuit?

Volts = Amps * Ohms Theoretically I wanted this (rounded): 3 V = 0.002 A * 1440 Ohms Realistically I got this because a limit of resistors I had (rounded): 3.206 Volts = 0.002 Amps * 1421 Ohms From ...
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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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4answers
2k views

Why does current only choose path of least resistance sometimes

Say we have the following setup simulate this circuit – Schematic created using CircuitLab Input is pulled high and current flows through it as long as the switch is open. As soon as it closes ...
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1answer
406 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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2answers
4k views

Calculating sum resistance of multiple series and parallel resistors

! I know how to find resistance, current, and voltage through series/parallel circuits. The problem I'm having is figuring which part of this circuit to simplify first. What is the correct order of ...
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2answers
48 views

Current in a closed DC circuit

I am in the process of learning the fundamentals of electricity, however I am having trouble understanding why there is no measurable current in a closed DC circuit when there is no power consumption. ...
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0answers
88 views

Two of the same resistors have different resistance?

I am doing some work on the electronics of a guitar and in doing so was testing some old circuitry. I noticed that there are two resistors each stamped with ‘223’. When checking the resistance of ...
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1answer
1k views

Convert transformer resistance data from Watts to Ohm

Short version: How can I convert transformer resistance values from Watts to Ohms? Long version: In PSS/E, transformer resistance can be entered as either per unit values (system base or transformer ...
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1answer
55 views

Can we get more current by reducing voltage on a power supply?

This is very basic question but I seem can't find the answer. All out there is theory, but no practical explanation about this. Assume I have a 10V 2A power supply. So in theory it outputs power of ...
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3answers
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What is a good resistor value for my circuit?

I'm trying to tap into my car's brake circuit to switch between receiving a wireless camera signal and powering my device. For this purpose, I connected a relay to the circuit via a fuse tap. It ...
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5answers
83 views

If Voltage determines current , a transformer regulate current?

Well , a transformer can regulate the voltage , increasing and decreasing it . And , if the voltage increase , the current too . So... a transformer regulates current too right? Sorry if its a ...
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0answers
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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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3answers
83 views

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
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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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2answers
95 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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2answers
72 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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How do I prove to my physics teacher that adding a battery in parallel doesn't double the current?

simulate this circuit – Schematic created using CircuitLab My physics teacher said that the current through the resistor is 4A because each battery has a current of 2A if hooked up to the ...
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2answers
57 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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2answers
123 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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2answers
118 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
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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1answer
36 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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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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3answers
63 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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8answers
46k views

Power's relationship to Resistance

$$ \frac{V^2}{R} = P = I^2 \cdot R $$ According to this equation, Power is inversely proportional to resistance on the left side and directly proportional to resistance on the right side. How can ...
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4answers
366 views

Calculating Necessary Resistance In Current Source Circuit

I have a problem where I must calculate the resistance required in R3 to have 1A flowing through the two 9.7V sources in the image below (i.e. Charging the batteries at a rate of 1A). I have ...
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3answers
121 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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2answers
701 views

How to calculate induced current?

Suppose we have a closed loop with two resistors in series and at particular moment in time the induced emf was two volts .i want to know why do we use ohm's law in calculating the induced current ?
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1answer
77 views

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
104 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
53 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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1answer
95 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
78 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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1answer
83 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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2answers
284 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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1answer
107 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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6answers
16k views

Ohm's Law confusion — can there be voltage without current?

I know there has been asked a similar question about this before but I still have some issues to understand the whole voltage and current thing. ( Current without Voltage and Voltage without Current? ...
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3answers
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
92 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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2answers
145 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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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
103 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
189 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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3answers
2k views

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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7answers
1k views

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
248 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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1answer
355 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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2answers
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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1answer
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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