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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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 ...
53 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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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://...
83 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 ...
106 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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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 ...
185 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 ...
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 ...
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 ...
214 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 ...
125 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 ...
45 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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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 ...
2k views

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 ...
129 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 ...
56 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; ...
1k views

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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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 ...
120 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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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, ...
79 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. ...
561 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 ...
538 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 ...
157 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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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 ...
55 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 ...
171 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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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 ...
344 views

Why can't I use Ohm's Law on my circuit?

In my circuit, I have 5V power supply and I have 200 ohm resistor. When I measure the current, it's 14.8 mA. Why can't I use the equation I = V/R, which is 5/200 = 25 mA?
129 views

Fuel sender - need something to convert ohms to volts?

I need to connect a cars fuel sender(ohms) to a analog input on a GPS tracker (volts) Here's the catch, in our tests most fuel senders we worked with seem to send the data as ohms/resistance However,...
43 views

How to calculate R for an AC load on a 3-ph system

I'm trying to calculate the resistors in an AC dummy load for a 3-ph system. A simplified schematic can be found below. The idea is to switch (with regular AC 1-ph contactors) some resistors on each ...
73 views

Find the current at the resistor

I've tried to divide current at 8A and then make a Kirchhoff voltage law between the resistor and dependent current source but I still can't solve it.
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How to read a multimeter (digital) — should I get 2A readings from a couple of AA batteries?

I have been using some old multimeters in a high school science lab. We did a current an voltage reading from a AA supply (two batteries) with a variety of resistors. In some cases a 1M resistor. I ...
118 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 ...
94 views

Voltage Drop doubt

In an ideal circuit with just a battery short circuited, where there is no resistance in the wire, why is it necessary to have resistance along the way? I understand Ohm's Law, and that the current ...
248 views

LED Blinking after replace

For clear any mistake, the question is: Why the LED started to blink after being replaced? The goal was to replace the blue leds with red leds, after replacing the leds one of them started to blink, ...
259 views

How do transformer obey Ohm's law?

I am honestly confused, A transformer "Steps up the voltage and steps down the current" or vice versa. So how does it obey Ohm's law? for example, a transformer with a winding relation of 2:3, should ...
172 views

Do rail gun systems require high voltage?

I couldn't justify, as to why most rail-gun examples I found would have high current and high voltage. When the rails & projectile can be designed to have low resistance by varying the volume of ...
165 views

If amps and volts can vary independently, how does Ohm's law actually work?

This is a very basic question as I'm just starting to get into things, but I've hit a roadblock with comprehending the definition of voltage as it relates to the relationship defined in Ohm's law. It ...
56 views

What is the difference between voltage across battery and voltage across a resistor?

simulate this circuit – Schematic created using CircuitLab I am doing an experiment for a lab and I am confused as to what they are asking. They ask to measure the voltage across the battery, ...
217 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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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 ...
219 views

Transistor driving LED

I have already asked a question regarding this problem but it was about a different thing, slightly. Here is the drawing of a LED driving circuit. The problem I have encountered with traditional ...
165 views

Same LED, different voltage drops with different supply voltages

I have an LED with no specs for it. I decided to measure the voltage drop across the LED, so I connected it to 5 V power supply and 325 ohm resistor. I measured the resistor with multi-meter, then I ...
97 views

Induction heater requirements

I am working on determining the specs needed for an induction heater I plan on buying or building. However, I’m having trouble calculating the potential current draw and wattage needed for my ...