Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

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 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 resistor on its own, and so they both have 2A of current…
Student
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Why don't we use low voltage Power Sources for high wattage applications?

Super nooby question involving Ohm's law, but this has been on mind this morning. Say I have a 60W device, and I want to power it. Usually this calls for a 120V source or something. However, why not use a 5V source and draw 12A with really low…
Capn Jack
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Where does U for voltage come from?

I believe in Europe the letter U is commonly used for voltage in (eg.) Ohm's law \$U = I × R \$. I think I understand where the letter V came from, commonly used in North America. But what's the story with U?
jippie
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Why does my 120V 40W lightbulb only have 26 ohms across it?

I thought that if the voltage source is 120V and the lightbulb is 40W then the current would be 1/3 of an ampere meaning that the resistance of the lightbulb would be 360 ohms. But when I checked it with my multimeter, it was only 26 ohms. The…
ratsmisimo
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Why do we need resistors in led

I've researched and it says that resistors limit the current flowing through the LED. But this statement confuses me because we know that in a series circuit, the current is constant at every point, so how come a resistor can limit the current…
vvavepacket
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accounting for LED resistance

I'm doing a simple lab (I'm a hobby EE) to reinforce my ohm's law math and learn a little about how to do proper measurements with a multimeter. I have simple circuit with a 2.2k ohm resistor connected in series with an LED. Everything works fine up…
Freeman
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Does a diode really follow Ohm's Law?

Does a diode really follow Ohm's Law? Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance,one arrives at…
Gabriel Staples
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How can a resistor affect current AND potential at the same time?

Though the resistor is always introduced as one of the most simple components it is the one which makes least sense to me. Ohm's law defines the resistance as$$R = \frac{V}{I}$$ this means that the voltage is defined as $$V = I \cdot R$$ and the…
bodokaiser
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Why is a 220 Ω resistor for this LED suggested when Ohm's law seems to say much less is required?

I have been interested in this particular switch with a built-in LED. According to the website, the forward voltage for the LED inside the switch is "about 3 V". It then goes on to recommend a resistor of ateast 220 Ω resistor as do some other…
Qu9ke
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Why does an LED have a maximum voltage?

When powering a simple LED circuit (DC power source, LED, resistor), does the supply voltage matter, as long as the correctly calculated current limiting resistor value is used? In other words, is there / could there be something inherently wrong by…
Geremy
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Why do diodes have a voltage drop?

Is resistance what makes a diode have a voltage drop? Or is it impedence? If it is electrical energy being converted to light, please tell me what this effect is called.
Vial
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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 drain pumps from most manufacturers have similar…
A. Ghioni
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How did scientists deal with electronics' problems before Kirchhoff and Ohm's laws?

Both physicists developed really powerful laws which still nowadays rule the electronic behavior of circuits. These help us every day to solve problems, calculate circuit variables… but how did engineers do it before the said laws were…
xvlaze
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Does a generator produce voltage or current?

I know that this question might sound very stupid for +90% of you, but my brain doesn't really get the electricity generation. The thing that I don't understand is what does a generator produce, voltage or current when it spins? Sometimes I see…
Physther
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What are the consequences of oversizing resistors?

When building a circuit to power an LED, we use Ohms law to calculate the required resistance, then to calculate the required wattage of the resistor. Suppose this formula dictates a 1/8 W resistor, and I instead use a 1W or a 100W resistor of the…
Elliott B
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