Questions tagged [power]

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Calculate the field efficiency factor for two long wires?

how can we Calculate the field efficiency factor for two long wires? field efficiency factor>>>>>>Eh=U/d>>>>>>η=Eh/Emax but i dont know how to Calculate the field ...
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1 vote
3 answers
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How can nuclear reactors control the exponential cascade of neutrons fast enough to prevent an explosion?

The Wiki article on nuclear reactor physics states that the average neutron lifetime in a typical core is on the order of a millisecond, the exponential factor is as small as 0.01, in one second the ...
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Understanding small DC motor curves (torque, efficiency etc)

I have a small DC motor/gearbox unit and the spec sheets is shown below. All* the units are measured at the gear box output, so 100 RPM would be 3,000 at the motor. I'm using it as a generator so am ...
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MOSFET pass short spike during power up

I discovered one feature. I've designed circuit for pulse generation and I discovered that it always pass one spike during power up. The circuit is consist of two sections. PMOS for Enable and PMOS ...
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Can I use a PWM motor regulator to control a LED string?

I recently bought some LED Christmas lights, but they are too bright. So I was thinking that maybe I could regulate the output by using a PWM regulator? My LED lights have an output of 30V from the ...
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What do the different "mA" versions of this "battery eliminator" mean?

Page in Swedish, but has a photo: https://www.jula.se/catalog/hem-och-hushall/hemelektronik/batteriladdning/batterieliminatorer/batterieliminator-409049/ This device allows you to select between 3-12 ...
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Household 3 phase devices

So, I'm not sure if this is the right place to ask this, but have been working on modifying a lawn mower robot that has, for roughly 3 years now been stored under less than favorable conditions. As a ...
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Everyday examples of hydraulic pressure drop generating heat

I'm interested in hands-on examples of voltage drop in electronics dissipating the energy as heat, and, thought that the hydraulics analogy, that is the same thing, might be a good way to intuitively ...
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Power systems unclear voltages

I was looking at this problem: "A balanced delta connected impedance load with (12+j9)Ω per phase is supplied by a balanced three-phase 60 Hz, 208-V source " I do not wish to ask for help at ...
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Line to neutral voltage in three-phase power systems

I have the book "Power system analysis and design" by Sarma. In his intro to balanced LN voltages, in chapter 2 p62 he states: $$V_{LL} = \sqrt{3} V_{LN} \angle30º$$ but later in the chapter,...
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Required Motor Torque [duplicate]

I am interested in constructing an robot which will be responsible for supporting a 200 pound load. There will be four wheels and the diameter of the wheels are 8 inches. The robot will be required to ...
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Battery size and maximal power output [closed]

Generally how does the size of the battery affect its maximal power output(together with other factors like materials, for instance)? Under the current engineering technology and with any possible ...
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1 answer
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What is the maximum distance for eavesdropping? [closed]

There is a closed question https://physics.stackexchange.com/questions/276667/what-is-the-maximum-distance-for-eavesdropping-sound-waves on Physics Stack Exchange and I thought this might fit better ...
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Devices powered and charged via electricity generated by human body

I came across articles like: https://www.sciencedaily.com/releases/2021/02/210210142049.htm https://pubmed.ncbi.nlm.nih.gov/27836601 and https://www.dailymail.co.uk/sciencetech/article-2004801/Weve-...
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Motor Power for vertical lift in linear slide mechanism

I want to pull up and down 10 kg metal cylinder at 7 inch vertically by using linear slide mechanism in 1 second. What should be the motor rpm, gear type, torque, watt etc? Otherwise how to calculate ...
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How to convert car power into energy (MJ) used per km?

I am currently attempting to do an energy audit regarding how much energy my car uses per kilometer. I am not sure whether my approach to this is right, and it feels like I have made too many ...
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5 answers
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How can I add the torque of multiple gears?

If I have 3 gears meshed with a gear in the center of the 3 gears as shown in the picture. all of those 3 gears are connected to different power sources. They are free to rotate in the same direction ...
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Are there any methods to figure out how aerodynamic a race car is without a Cd number?

For the top speed of a car, I believe it's usually limited by drag and horsepower. However, I've also learned that gearing can affect the top speed and acceleration of a car. Are there any methods to ...
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3 answers
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Does more downforce affect the acceleration and top speed?

How can downforce make a race car faster, apart from being faster around corners? I just recently learned that downforce can help a car accelerate from 0-60 mph faster. Usually, I thought drag didn't ...
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1 vote
3 answers
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Do gears affect top speed?

Do more gears affect the top speed/acceleration of the car in any way? I know the gears won't increase hp since more gears would increase RPM but would decrease torque.
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5 votes
1 answer
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Alcohol as a working fluid?

Alcohols with their lower boiling point and overall non-toxicity, could they be used as a turbine working fluid instead of steam water?
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2 answers
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How to quantify motor performance?

I notice that motors are often described by their power rating. So, for example, you might have a motor that is described as a 1 HP motor. However, that is actually not a complete statistic because ...
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How are NASA's mars rovers able to operate with such little energy?

The latest Mars rover being, NASA's Perseverance, uses the Multi-mission radioisotope thermoelectric generator, which has a maximum power output at the beginning of it's operational life of 125 watts, ...
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Charging a 2020 M1 Macbook Pro from a low-voltage solar array

I'm working on a small project to mount solar panels to a Macbook case which would allow it to charge/offset battery consumption. I noticed that I was able to power the Macbook on public transport ...
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2 votes
1 answer
434 views

How much power does it take to supply a laser which delivers 100 watts? [closed]

To enable the functioning of a laser which delivers--on average--100 watts of energy in its beam, how much power does it take? (Does the 2nd law of thermodynamics dictate that the average power ...
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Power calculations for starter motor designing [closed]

Let's consider an IC engine standard type motorcycle. What is the power needed from the starter motor to start it's engine? Please make all the calculations by taking suitable assumptions like the ...
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How to drive variable power (up to 1500w) to a grill heating element [closed]

I have a heating element like the following: which is rated to 1500W. I need to be able to drive up to 1500W of power to it, but potentially less. I will be plugging it into a 120V wall outlet. I am ...
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1 answer
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how much power is needed to move a linear axis

Ι need help calculating the power usage for a linear axis motor. it must move up and down at a maximum speed of 0.5 m/s a load of 50 kg What I did so far: The load (i.e. weight) acting on the motor ...
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3 votes
1 answer
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Does electricity go through non-metal materials or not?

Ever since I was a little boy, I've always had this idea that electricity can only go through metal materials. For example, if I put a 100% metal screwdriver into the socket in the wall, I'm going to ...
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1 vote
0 answers
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Power distribution problem in multi-camera usb array

Problem Summary My MacBook Pro (development system) can successfully capture images from 24 cameras in the multi camera assembly we have assembled. But when our assembly is attached to a new Raspberry ...
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1 vote
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Why doesn't the Stress Power in the theorem of the expended mechanical power contribute to the kinetic energy?

The following is the formula of the expended mechanical power: $P(t)$ $=$ $\frac{d}{dt}$ $\int \frac{1}{2} \rho\ v^2 dV$ $+$ $\int \sigma \colon d\ dV$ where $P(t)$ is the mechanical power entering ...
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2 votes
2 answers
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Sun as water pump in underpressure water power circle

Introduction A water storage power plant pumps water up to a reservoir when there is more power available than needed and lets the water flow down when power is needed. For pumping water up, ...
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1 answer
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Is there a positive displacement compressor that can rival axial compressors in terms of air mass flow to weight ratio?

Is there a positive displacement compressor that can rival axial compressors in terms of air mass flow to weight ratio?
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1 vote
2 answers
186 views

Integrating torque over time

I cannot seem to be able to find which unit applies to the integral of torque over time. If you compress a bracket shaped load cell, you exercise torque on it, say 5 Nm. Now, say you do this for 5 ...
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How can you calculate the specific fan power of a fictitious HVAC system?

I am working on a concept involving an HVAC system drawing air in from outside. Known information: Air flow rate (calculated), change in pressure accross fan (given) and total efficiency (assumed). No ...
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1 vote
2 answers
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What happens if an entire country turns off all lights and electric devices during peak consumption hours? [duplicate]

I've been reading about smart grids but I studied Computer Engineering and my already limited knowledge of power systems is very rusty. I keep hearing that traditional power stations have to adjust ...
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1 vote
1 answer
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Weibull distribution Units - ENGIEQSOL

I am using Engineering Equation Solver, and it has been telling me the units of my distribution are inconsistent. According to a the book I am reading, I think it should be unitless (as it is a ...
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Why am I getting wrong value here?

A man threw a ball with force 10 N to two displacement of 5 m and 10 m. F = ma, so let mass be 2 kg. a = 5 m/s2. Work done = 10 × 5 and 10 × 10 = 50 Nm and 100 Nm. Now, since a = 5, I assumed that ...
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Can we say kinetic energy is tangential K.E?

I saw this in my textbook that $\dfrac{\text{d}K}{\text{d}t} = \dfrac{\text{d}(1/2mv^2)}{\text{d}t}= F_t v$ where $F_t$ is the resultant tangential force on the body. Now, let $F_t= F\cos\theta$ $$\...
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Overcurrent protection, limit for nominal current or stall?

Background: I'm currently working on a robotics design that will drill through soil. I have selected a 48V motor who's nominal current is 3.17A and has a stall current of 42A. I will be driving the ...
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2 votes
3 answers
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Relation between armature voltage and mechanical power in electrical Engineering

I am searching for an effect chain that leads to the mechanical power $P_{mech}$ of a DC motor, starting with the applied armature voltage $U_{A}$. My request also includes all the electrotechnical ...
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22 votes
4 answers
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How does turning off electric appliances save energy

We all know if we use less electricity we save energy. But the energy we're getting is result of burning (not necessarily the literal meaning) the fuel. Even if we don't use that energy that fuel is ...
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1 vote
1 answer
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Is using a 4x4 bolted to the face of 2x12 enough?

I am working on a project that has three 2x12’s supporting a load of 12,000 lbs. similar, but not exactly, to how joists support a house. The 2x12’s are supporting about 6,000 lbs. on each end. The ...
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2 votes
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Why 'battery storage power stations' use mainly liion batteries?

As I understand liion batteries have lower lifetime, than LiFePO4. Why would such big stations use liion batteries then? Wouldn't replacement cost large amount of money? And how long those liion ...
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3 votes
1 answer
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Power a microcontroler with a motorcontroller?

I have a motor controller that operates at 10-50V and draws 5A controlling a 3V motor that draws less than 1A. I had a an idea where I want to try to use a microcontroller to control this set up. The ...
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1 vote
1 answer
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Does the strength of a servo motor depend on the motor or the power?

I am making a life-size robotic dog, and i am having trouble with getting it to walk as it is too heavy for my 4 micro sg servos. Can i make the servos more powerful with more power? If not i can just ...
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3 votes
0 answers
111 views

PMDC Motor Characteristic Graph

I am trying create a graph similar to as shown below. However, I am confused as to how the torque is related to the characteristics. The graph that is to be replicated for certain parameters: The ...
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2 votes
1 answer
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Transformer Phase Fault

I have a transformer for troubleshooting. It is a 3 phase DELTA-WYE Step down (11KV/400V) transformer, the low side voltages (secondary) are Line to line voltages: RED-YELLOW : 400 V YELLOW - BLUE :...
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1 answer
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What happens if you wire two solar panels in series and parallel at the same time?

Will anything bad happen? Or is it safe.
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2 votes
1 answer
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AC Harmonics on a system appearing as DC

I have a theoretical question about harmonics and DC. Given I have a circuit which has a power supply providing an AC input(230Vrms @ 50Hz), this then goes into a load which, takes this supply ...
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