Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit 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.

0
votes
2answers
76 views

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 ...
0
votes
4answers
110 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 ...
0
votes
1answer
73 views

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, ...
-3
votes
1answer
41 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 R2/(R2+R1)*12V as voltage. Then, as I know that it ...
3
votes
1answer
499 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 ...
1
vote
1answer
26 views

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 ...
0
votes
1answer
85 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 ...
0
votes
5answers
130 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. ...
1
vote
2answers
68 views

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 ...
0
votes
2answers
52 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 ...
1
vote
2answers
62 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 ...
0
votes
1answer
36 views

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 ...
0
votes
4answers
276 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?
1
vote
1answer
85 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,...
0
votes
0answers
40 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 ...
-1
votes
1answer
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.
0
votes
3answers
90 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 ...
0
votes
3answers
86 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 ...
0
votes
2answers
85 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 ...
2
votes
2answers
202 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, ...
0
votes
2answers
152 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 ...
0
votes
2answers
94 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 ...
2
votes
4answers
159 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 ...
0
votes
0answers
53 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, ...
1
vote
2answers
55 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 ?
0
votes
1answer
69 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 ...
0
votes
4answers
165 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 ...
1
vote
3answers
128 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 ...
2
votes
1answer
77 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 ...
-1
votes
4answers
194 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, ...
0
votes
1answer
155 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 ...
0
votes
6answers
137 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 ...
0
votes
6answers
171 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 ...
1
vote
1answer
74 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 ...
0
votes
1answer
239 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?
1
vote
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 ...
0
votes
5answers
138 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. ...
-1
votes
2answers
102 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. ...
0
votes
0answers
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:
3
votes
4answers
376 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 ...
0
votes
0answers
29 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 ...
1
vote
1answer
130 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 ...
-3
votes
1answer
603 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.
0
votes
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. ...
0
votes
1answer
21 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 =...
1
vote
3answers
3k 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 / ...
2
votes
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 ...
0
votes
1answer
66 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 ...
15
votes
7answers
5k 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 ...
0
votes
6answers
258 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 ...