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
71 views

Limitations Of Ohms Law [closed]

Sometimes i think why the heck this ohms law created to make troubles for us, as nowadays i am deeply working on Basic Electronics so there Ohms law actually sucks... I was studying transistor ...
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58 views

Effective resistance from a random resistance network

I am trying to calculate the equivalent resistance from a random resistance network formed by carbon nanotubes (CNTs.) I have a MATLAB program where the CNTs are randomly distributed inside a volume. ...
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Can anyone help clarify all the values on these rating labels?

I am doing some small asssignment for my class. But I am bit confused about the power ratings on these two labels. For example, the first label, I used P=VI to calculate power. So P= 12 * 1= 12 [W], ...
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How to test a Peltier module TEC1-12705 to determine if it works as intended?

Background: The module comes from a 70W mini-cooler which doesn't really cool anymore. I took it apart and got the module out, I could read the model TEC1-12705 from the module itself. The ...
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Weird MOT current measuerements

I have MOT transformer, which I want to use for DIY spot welder. I measured 0.85V on one turn of primary open circuit, it means cca 2.55V on three turns etc. This seems ok. What I do not however ...
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AC parallel and series circuit

I have this AC circuit: simulate this circuit – Schematic created using CircuitLab I have found VA which is \$222 \angle-119 mV\$. The current flowing through the inductor \$IL = 2.6 \angle-89 ...
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1answer
34 views

How to determine what voltage and current I should use for a Kanthal heating element?

I'm in the process of making a plastic forming "tool". It has a hot wire inlaid into the top. I have not come up with the power supply yet but have a few iron core transformers laying around....
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49 views

Using KCL, KVL and Ohm’s Law find I0 in the circuit in Fig.1.1

I have spent more than 8 hours studying KCL and KVL and Ohm's law but I still can't solve this : If anyone can help me understand how to find I0, Ix and 2Ix I will really appreciate it.
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67 views

How to choose a perfect resistor to LEDs to get same brightness?

I'm using 5 different LED to indicate water level. I used a 330ohm resistor to all LEDs. Some LEDs glow brighter some are less bright. How can I calculate an exact resistor value to my LEDs to get ...
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1answer
59 views

INA219 Voltage measurements meaning

I have a battery holder, 3 x 1.5V AA, connected to a resistor (100 Ohm or close), LED and Adafruit INA219 breakout board. The bus voltage reading from the INA219 reports 1.0V. Where does this number ...
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80 views

Limit current to a load

I'm making a little heated greenhouse. I have three 1.2 ohm 5W resistors and a 5V 1A power supply. Everything is controlled by my Arduino through a MOSFET. Now, I would just need 5W of power to keep ...
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54 views

Current to voltage circuit

I'm currently doing a project that consists of testing bio-implants to see if they are still good to use. For this, I have to measure the impedance of the implant from frequency starting at 10Hz to ...
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47 views

How to calculate the resistor value necessary for the columns 8x8 led matrix?

I am building an 8x8 led matrix using 5mm LEDs (3.2V, 20mA). I connect it to the arduino UNO through the I2C using the GPIO expander MCP23017. The circuit is as follows: A matrix column is made up of ...
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35 views

Analyzing a circuit with 2 voltage sources

This is a problem given to us for homework: This is the first question I've got that has 2 power sources and I'm stuck on calculating the potential difference and current through R3, R4, and R5. I ...
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56 views

House refurb rewire - low current?

So we've been renovating (virtually new everything) a 1930s semi that hasn't been modernised since it was built and hadnt been lived in since the 70s. Naturally a full rewire was high on the agenda ...
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131 views

Ohm's law paradox?

I have a chain of 4 single resistors in series. Call them R1, R2, R3, R4. When I measure the total resistance from top to bottom, then I get the same result as if I measure each pair of resistors: (R1+...
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Current rating of a circuit

Need advice: I have a circuit board that is BMS/PCM for a battery as a protection circuit board. The circuit has an IC and has one MOSFET, transistors, and diodes. I want to know how can I increase or ...
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110 views

Why is the voltage across my nichrome wire so low?

I have a 37 AWG nichrome wire (0.6 mm diameter) with 5 ohm (about 3 m wire) resistance, 12 V DC supply with max 1 A output. I only measured 1-3 V across the nichrome wire, the wire does warm up but ...
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1answer
112 views

Why is my multimeter reading such a high/erratic current?

Newbie to electronics here. I have a simple circuit consisting of just a 9V battery and an 820 ohm resistor. I was trying to measure the current with a multimeter (by opening the circuit between the ...
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1answer
55 views

Different answer from power equations

Imagine a circuit like this: 6 red leds with a Vf of 1.8V are wired in series with a resistor. Vcc is 12v. To acheive a current of 10mA, you would do (12-10.8)/0.01 = 120 so 120 ohm resistor. Now to ...
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3answers
478 views

Why does this current not match my multimeter?

Newbie to electronics here! I have an Arduino Uno with a 15 Ω resistor connected to the 3.3 V pin, on my multimeter, it gives me 3.2 volts. If I use this calculator: https://ohmslawcalculator.com/ohms-...
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Is power proportional to V or V^2?

I am confused on this. We know that P = IV and V = IR. That means P = V^2/R by substitution. I understand that by that second equation we can say "power is proportional to voltage squared" ...
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39 views

DC Circuit Analysis from Sergio Franco Book : Electric Circuit Fundamentals

If current source is absorbing power then the polarity wise Vb will be +ve.Then i calculated the value of Vb=4 x 2A = 8V Va= Vb + (20*2) = 48V and Vs = 164V Thus for current source to absorb power of ...
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Circle with arrow symbol interpretation in circuit

I am trying to find all currents in this circuit: (Question 19 from https://www.allaboutcircuits.com/worksheets/algebraic-equation-manipulation-for-electric-circuits/) Although I'm familiar with Ohm'...
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Calculating the power lost per foot from “\$I^2R\$ losses"

I am currently studying The Art of Electronics, third edition, by Horowitz and Hill. Exercise 1.6 says the following: C. Power in resistors The power dissipated by a resistor (or any other device) is ...
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487 views

How does power remain constant when powering devices at different voltages?

As per the below image, increasing the voltage in a circuit with just a resistor results in an increase of current and therefore power. However if I have a circuit where I am just powering a DC device ...
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119 views

Ohm's law when there's no resistance [closed]

ohm's law says that V = I*R And so I = V/R But what happens if we have a circuit with 0 resistance? That would make everything else 0. What does that mean?
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125 views

Voltage drop through a resistor for a single charge, contrasted to a non-ohmic component

Recently I have been reading about how transistors and diodes only drop a limited amount of voltage across their leads for a wide range of currents. So the voltage drop per charge (at a given ...
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34 views

Resistor on data line between SK6812MINI-E and an MCU

Im getting pretty confused by the resistor that is supposed to be between the DIN of the first SK6812MINI-E and the pin of the MCU. The LEDS are being powered by a 5V 2A power supply (but should only ...
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2answers
64 views

Incorrect amperage readings, possible faulty meter?

I have a very simple circuit: a 9V battery is connected to a 1500ohm resistor, which is connected in series to the multimeter and back to the battery. simulate this circuit – Schematic created ...
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2answers
596 views

Is it possible for the system of equations of an electric circuit to not have a unique solution?

When using Kirchhoff's circuit laws and Ohm's law to model the system of linear equations corresponding to an electric circuit (so far, circuits involving resistors and sources only), I haven't been ...
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Is the electric field in a wire constant?

If \$V=I\cdot R\$ according to Ohm's Law, that implies that \$\frac{\mathrm dV}{ \mathrm dx} = \frac{I \rho}A\$ across an infinitesimal length of conductor, which is constant at all points along the ...
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118 views

voltage regulators: How does Ohm's law apply here (and how not to fry an ams1117)

Very basic noob question here, asking for an analogy rather than a 'it's law xy': I used an ams1117, 2.5V, sot223. To test it, I used an usb cable 5V and plugged it into my phone charger (rated 2A) ...
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2answers
124 views

Superconductors vs Ideal conductors

I have always assumed superconductors and ideal conductors as the same thing, but recently I found out that they are not. I tried to look up their differences on the internet, but I got only mixed up ...
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4answers
87 views

Joule heating /Ohmic heating

I have trouble understanding why Joule heating is called ohmic heating. Also the joule heating effect establishes direct relation between current and resistance(as more current more collision more ...
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1answer
56 views

Need proofing on this 12v battery protection circuit

I am making a battery protection board for my 12v battery. The amperage pulled from the battery could go up to as much as 20A. I want the Arduino (connected to the protection board) to activate the ...
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66 views

Voltage in a ring circuit with induced current [duplicate]

Supposed I have 3 resistor, R1=1 Ohm, R2=2 Ohm, R3=3 Ohm. I connect them with copper wire to form a ring R1-R2-R3-R1 I used a device to generate changing magnetic flux in that ring. So there must be ...
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2answers
138 views

How to show that it is not possible to exceed the power rating of a 1/4 watt resistor of resistance greater than 1k?

I am currently studying The Art of Electronics, third edition, by Horowitz and Hill. Exercise 1.5 says the following: C. Power in resistors The power dissipated by a resistor (or any other device) is ...
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5answers
435 views

Finding current through LEDs in series-parallel circuit

I'm stuck confirming that the current pulled in a circuit will be 15mA. If I have hypothetical LEDs that pull 15mA each from 1.8V, and they are put in parallel (I know this is not a good idea, but ...
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Calculate current through a resistor attached to an ADC?

I have a resistor, R1 = 100 kΩ, connected between a: DAC PIN_1 outputting 1.34 V ADC PIN_2 At PIN_2 I measure 0.57 V. Can i model the circuit as:PIN_1 -- 100 kΩ R1 -- PIN_2 -- R_ADC -- GND? For V1 ...
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4answers
122 views

How is the current through this resistor not obeying ohm's law?

In this video, https://www.youtube.com/watch?v=ks_VShSgPns, a 220 ohm resistor is connected across a 5V DC source (the source happens to be oscillating between 0V and 5V but that's besides the point). ...
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3answers
213 views

Is resistance the derivative dV/dI or the ratio V/I?

I'm trying to understand the justification for turning off independent sources when calculating the equivalent resistance in Thévenin's theorem. This answer explains has a good explanation but it ...
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1answer
69 views

Reduce DC power supply for battery charging

I have a DC power supply from either a WIFI router or printer (not sure) rated for 13.5V @ 1.2A output. This is a replacement charger for an electric ride on car as it was originally 6V and I've ...
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Why does voltage drop across resistance contradict Ohm's law?

Very basic question here. I have been learning a ton about Ohm's law, and I don’t seem to ever be able to completely understand it. One of which I am getting particularly confused about is voltage ...
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2answers
115 views

Where does Ohm's Law, Kirchhoff circuit laws, etc, come from? [closed]

I know that these various laws that we use are often commonly accepted in practice but I am always curious how far down the rabbit hole you can do until you hit something that you just accept as true. ...
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67 views

How is the current adjusted from a power bank with adjustable current?

When using a power bank with adjustable current I'm just wondering how the current is adjusted? it can't be anything to do with resistance of the recieving component because this would be constant, ...
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125 views

Battery Charger in Parallel with System Load Current Sharing - Power Path Control

Currently, I'm building a project which can either run connected over USB or via a battery. The project itself switches between either high current draw at around 450mA or low current draw at 50mA. ...
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2answers
79 views

How to compute the resistance and voltage of this schematic?

I have the following diagram I've set up in a simulator: However I have no idea how they get 3.75V at that point (the upper left spot is a voltage reader) nor do I really even know how to apply Ohm's ...
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3answers
42 views

Need assistance to understand Power and Ohm's Law

Hello I'm looking at a light bar on a vehicle and the specifications say it draws 7.5A at 9-32V and the light bar says it has 36 x 5 Watt LED lights which would make a total of 180 Watts that this ...
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4answers
151 views

Input voltage control by resistor, is this method is correct or not?

In my application I have a requirement to switch 40V to 5V with the help of a linear voltage regulator. My load circuit consumes approx 7 to 8 mA. Due to the unavailability of any specific model of a ...

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