# 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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### Design of a nichrome heating element - achieving predetermined power dissipation

I want to make a nichrome heating element with 1500 watts of heat being produced while running on 120v AC. This will be part of a air heater as a fan drives air over a circular coil of nichrome wire. ...
879 views

### joule heating - transmitting power at higher voltages reduces resistive loss?

electrical engineering hopeful here. Can someone explain with math how transmitting power at higher voltages reduces resistive loss? I know Joule's Law Power is proportional to (I^2)*R lets say ...
671 views

### I do not understand what power actually is

I realize this is probably a super common question, but I have to put it in my own words. I try to understand ohm's law with the water analogy. Two tanks with water, one with a higher level than the ...
87 views

### How would i go about finding Rl when rl is r3

How would i go about finding Rl :/ I'm so lost iv looked for examples and all they have done is confuse me
2k views

### Does current source affect flow of current in circuit with a variable resistor?

Suppose you have a current source in series with a resistor R the current through the R resistor would be the current generated by the current source. How would the current through the circuit change ...
600 views

### Application of Ohm's law / Conservation of Energy

I am taking my first Engineering Electronics class, Engineering Circuits I. I seem to be understanding it, but this one example confuses me somewhat. The simplest manifestation of Ohm's Law (...
7k views

### Voltage drop measurement result doesn't match my theoretical calculation

I have a $1.5\Omega$ resistor and $8.84V$ battery. My multimeter tip's resistance is $0.3\Omega$. I've tried to compare the calculated voltage drop (which is $8.84V$) with the measured value. ...
918 views

### Why does the voltage changes in this simple circuit?

I'm beginning to learn electronics, and there's something I just can't grasp. I was told that a high resistance in a circuit would lead to a smaller current passing through it, but the voltage would ...
4k views

### Why does an infinitely decreasing resistance infinitely increase current?

So I have been mulling over Ohm's law for hours today. It makes sense to me that the current gets bigger as voltage rises, since the voltage is supplying more electrons and current is the number of ...
57k views

### 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 ...
675 views

### Trying to understand why power equation and ohm's law equation aren't agreeing

Hobbyist EE-in-training here. I've been doing some simple problems to reinforce my knowledge of ohm's law and I've run into a snag - A stereo speaker has a resistance of 8.00 Ω. When it is ...
567 views

### How can current-limiting supplies be possible?

Knowing Ohm's law, the current drawn is directly proportional to the resistance. In some power supplies, you can limit the current. Let's say the voltage is 12 volts, it supplies 1 amp, and the ...
3k views

### How do I pick the right resistor for an optoisolator given a desired current?

This is a follow up to this question, but isn't specific to the other one. This is both an ohm's law question and a 'how does one interpret data sheets' question. I want to minimize the current I ...
1k views

### basic math question about voltage, ohms, resistance

total n00b here. After working on several projects by copy & paste from other people's schematics and code, I'm finally digging in and learning some of the math to know what I'm doing. If I have ...
19k views

### Why do LEDs not obey Ohm's law?

In a previous question, it was brought to me that LEDs do not obey the Ohm's law. (See Calculate expected voltage around a resistor) Simply put: how is that? What makes them behave so differently? ...
4k views

### Calculate expected voltage around a resistor [duplicate]

It's been a few years since I first studied the Ohm's law at school. Now I'm really getting into electronics, and I must admit a part of it still puzzles me. I know this is kind of a strange question,...
38k views

### How is current lowered as Voltage is increased in AC power transmission

I was reading about power transmission on wikipedia and came across the explanation of the efficiency of AC power transmission that said power in the load = (I^2)* R while power transmitted= IV. The ...
210 views

### Voltage distribution between components

I often see the same method for computing voltage distribution in electronic circuits implying components whose V-I curves are not trivial. For example, in a circuit implying a resistor and a LED ...
17k views

### 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.
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### Maximum power for Arduino Monster Moto Shield

I'm reading the specs for the SparkFun Monster Moto shield which specifies that Max Voltage is 16V Maximum Current 30A Given Ohm's law, does that mean that the maximum power is 480 watts? That seems ...
2k views

### Should I use a resistor in this scenario?

I am building a IR pen and wondering if I need a resistor for this. Here is my specifications for my IR LED: Forward Voltage: 1.2 V Forward Current 100 mA So on and so on. I am powering it with a AA ...
219 views

### How to prevent a resistor receiving a too high power?

If a circuit was creating 0.3 watts, and resistors rated for 1/4 watts were used, what would be the easiest way to make it stay inside the rating? Would it be to, say, connect two resistors of twice ...
5k views

### A christmas light bulb question

This may look like a homework, but it's not. Actually it is related to Christmas. My Chrismas lights in front of the house are constructed from segments. Each segment consists of 16 incandescent light ...
240 views

### Reading datasheets and applying Ohm's Law

I have a CPLD that wants +3.3v and has a maximum allowable current per pin of 8ma. I need to supply a clock signal. The oscillator I selected accepts 5v and outputs 5v-ish levels. I'm finding it ...
2k views

### LED current limiting resistor and Ohm's Law

Yesterday I was trying to figure out how many ohms of resistor should I be using for my LED, and found this post right here in the forum. The formula states that one should subtract the voltage drop ...
745 views

### Triac datasheet values

I have a Triac that I want to use to control low voltage (~16 V) AC. The data sheet is found here. It specifies that the peak gate voltage is 5 V with a peak current rating of 2 A (which seems quite ...
40k views

### How do I calculate the necessary resistance for a voltage divider?

I’m self-taught, and this is a little bit of a thought experiment for me to understand Ohm’s Law better. I have a very simple voltage divider. Given a 15V DC input, each of three 4.7KΩ resistors ...
41k views

### Potential difference across one resistor with and without a known current?

Okay imagine you have a voltage supply of 10V and one Resistor of 5 Ohms. Now find the current : I=5/10 = 0.5A So potential difference across that resistor : V=IR=10V .. which proves this statement ...
4k views

### Sharing a pull-up resistor

I have two IC chips. On one chip I have one 10K ohm pull-up resistor and on another chip I have three 10K ohm pull-up resistors. At first I was using four through hole pull-up resistors. Then I ...
12k views

### How to choose correct resistor with proper wattage and ohms for 6 leds connected in a serial circuit?

Let's suppose I've six LED lights with each 3.2 Volt and 20mA and all six of them are connected in one serial circuit. I know there is better setup but for this I'm using this circuit setup. I'm ...
29k views

### How to calculate current and voltage draw of a single resistor circuit?

If I have a single 270 ohm resistor connected in a circuit to a 3.3V 50mA power supply, how can I measure the voltage and current for the resistor? I'm familiar with Ohm's law V=IR, where V is the ...