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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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218 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?
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1answer
77 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,...
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37 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 ...
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1answer
72 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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3answers
87 views

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 ...
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3answers
83 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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2answers
80 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 ...
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2answers
187 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, ...
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2answers
117 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 ...
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2answers
78 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 ...
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4answers
151 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 ...
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0answers
52 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, ...
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2answers
38 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
63 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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4answers
141 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 ...
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3answers
120 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 ...
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1answer
71 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 ...
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4answers
182 views

Ohm's Law and Death [duplicate]

So I bought an Arduino today, my high school grades were terrible but I decided to dive into electronic engineering anyway. I am a total noob so please forgive me. So Ohm's law states v = R * I, ...
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1answer
127 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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6answers
126 views

Why doesn't voltage drop across this resistor when transistor is off?

The following excerpt from a book explains the functioning of the circuit below: When V_in < V_th (device threshold voltage), the supply voltage (V_dd) is measured at the outlet. When V_in is ...
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6answers
146 views

why does a step up transformer cause lower currents?

The usual answer I hear is because power needs to be conserved, but I dont find that answer satisfying. Normally if I were to double a supply voltage in a circuit, then I would expect twice the ...
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1answer
73 views

Measured amperage differs greatly from my math

I've got the following circuit: simulate this circuit – Schematic created using CircuitLab It works. The LED glows nice and bright. However my math doesn't match the readings I'm getting from ...
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1answer
144 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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2answers
40 views

Can a power supply be too powerful for a device assuming that the power supply is at operating voltage of the device? [duplicate]

Let’s say a device’s operating voltage is 5V and maximum current that it can draw is 5A. Is it possible for a 5V power supply to have very low internal resistance such that a device that operates at ...
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5answers
133 views

Why can't you just reduce the current instead of the voltage?

Why does voltage even matter, if it's the current that goes through a circuit? I understand the relationship V = IR (I think) and that increasing the voltage (pressure) will increase the current. ...
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2answers
99 views

Double the voltage did not double the amps?

I have two brand new AA batteries. I measured the voltage and current of each battery and they are both 1.5v and 5A respectively. I connected these same batteries in series and I measured the voltage. ...
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45 views

How to find the current value in this circuit?

Here is the question i am getting how to proceed after finding the voltage My attempt : Next part of solution:
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4answers
370 views

How does electrical power relate to Ohm's law?

I have some difficulty grasping these concepts. Let's say, for example, a power source of 10W operating at 5V is connected to a load of 0.5 ohms. According to Ohm's law, it is expected that a current ...
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0answers
28 views

Verilog-A Current/Voltage/Power Inconsistency

I'm simulating a phase change material in Verilog-A and need to calculate the power across the material. The material is a resistor, so it satisfies Ohm's Law. Therefore, P = IV = (I^2)R = (V^2)/R ...
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1answer
129 views

Do I understand Ohm's law correctly?

I was reading a bachelor's thesis and it mentioned some technical details of a heated plate. Part of the technical details: MK2b Dual Power Technical Details [7] ...  Power Input: 12V or ...
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1answer
486 views

What can cause a resistor to become non-ohmic?

Can anyone help me find some causes as to why a resistor may become non-ohmic? Thanks in advance.
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2answers
1k views

What is the Danger in Plugging an 4 Ohm Speaker into an 8 Ohm Amplifier?

I know it is a commonplace warning not to plug in a 4 ohm speaker to an amplifier rated for 8 ohms. I am wondering what is the actual danger that is presented by doing this in an electrical sense. ...
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1answer
20 views

Power up a motor/pump

I have a pump (6-12V 4-5W) that i want to power up with a generator (9V 1.5A). I've calculate the current needed with : I = 5W/8V = 0.55A. Next i've calculated the resistance needed : R = 9V / 0.55A =...
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3answers
2k views

Max Voltage for Speaker of Given Power Rating

I have been looking into the design of loudspeaker drivers and would like to know how to determine the maximum voltage which can be delivered to a given speaker. From Ohm's law we know that P = V^2 / ...
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1answer
1k views

How many watts does tweeter needs

I have a speaker with the following specs: Max. power - 600W Impedance - 4~8 Ohm Freq. response - 45Hz-20KHz Sensitivity - 98dB/W/M The tweeter of the right speaker is not working so i want to ...
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1answer
63 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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7answers
4k views

Ohm's law doesn't seem to be working for this electric motor

I'm a beginner in this field so please forgive me if I'm confusing with my question. There is a component that I can't understand with Ohm's law which is a washing machine drain pump. Washing machine ...
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6answers
246 views

Smallest possible resistance (highest current) [duplicate]

I'm new to electronics and I've been familiarizing myself with some basic formulas, specifically Ohm's law. It seems to imply that if resistance is smaller than 1, let's say 0.00001 Ohm, then I can ...
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1answer
60 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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6answers
287 views

What is the voltage potential of ground during a short

During a short, is it possible for the voltage potential of the ground to change? Say for example, we short a 9V battery, how does the ground stay at 0V and not become 9V?
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4answers
84 views

High voltage, low current and vice versa

Can someone please explain to me in simple terms how is it possible to have high voltage and low current and low voltage and high current and what actually does harm to human body. Here is what I don'...
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4answers
119 views

How is it possible to have high voltage that is safe?

I am aware that current is very dangerous and only 0.2 amps is enough to stop a heart. However I always see that high voltage is dangerous. Tasers produce a high voltage but since there is low current ...
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2answers
93 views

resistance and current [closed]

I struggle to understand how if I increase the resistance in a circuit, it requires less current, based of ohms law.
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4answers
218 views

What is voltage exactly? [duplicate]

First, let me start off by saying that I have read the answers to this question (which is the same as mine), but the answers basically explain the different ways voltage is created or compare it to ...
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4answers
961 views

Why are voltage and current directly proportional? [closed]

So, I thought I had an understanding of Ohm's law, but after thinking deeply about it, the direct proportionality between voltage and current doesn't make a lot of intuitive sense to me. So, when I ...
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3answers
167 views

Is it possible voltage without current and opposite [closed]

I got really surprised by seeing this possibilities from a power, energy calibrator is it really injecting it by violating the laws what we use in practice? See the photos? If anyone knows it please ...
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5answers
251 views

Beginner Question about the logic behind Ohm's Law?

In all the physics i learned and practiced many subjects But understanding Ohm's law used to be a big problem for me... Here is what i mean : We have a 5 volt battery. And a 3 volt/ 20 mA led. So ...
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18answers
22k views

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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3answers
668 views

With parallel termination of a transmission line, why does the receiver see the full voltage?

With parallel termination of a transmission line, the line characteristic impedance \$Z0\$ is matched with the pull-down resistance \$Rt\$. But, in that case, shouldn't the receiver see half of the ...
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4answers
326 views

Circuits explained without analogies [closed]

So, I am trying to fully understand circuits without the use of analogies like "voltage is like a waterfall" or "a battery is like a pump," since I've heard that those analogies break down when we get ...