# Questions tagged [power]

The time rate of change of energy

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### Help me understand power and torque [closed]

I'm trying to understand power and torque relationship in terms of cars. Let's assume we have a four tracks with a load that needs a total of 1000N to move. First one has 1000 Nm and 1000W Second ...
1 vote
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### Power dissipated in a circuit

If total power dissipated in a DC circuit is given by $P = VI$ and power dissipated as heat is given by $P=I^2R$, since these are numerically equal, wouldn’t that mean all the power is dissipated as ...
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### What happens to laser power when resonator cavity length increased?

I am working with a He-Ne laser. What I have noticed, is that when resonator cavity length is increased (by moving on of the mirrors), output power goes down. What could be an explanation to that? ...
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1 vote
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### Average of calculated quantity of discrete data

Let's say I have two discrete series of a physical quantity, current I and voltage V taken at the same time interval in a DC circuit. Now, I want to estimate the average power P over N measurements, ...
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1 vote
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### Spectral representation of a white stationary process

I am trying to better understand the spectral representation of stochastic processes. From the book "Spectral Analysis for physical applications" by Walden and Persival: The spectral ...
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1 vote
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### Why can't I balance the units in the equation for power of a sound wave?

According to this answer (source), the time averaged power $P$ of an acoustic wave is: $$P = \frac{1}{2} \mu v \omega^2 A^2$$ Where $\mu$ is mass density of the medium, $v$ is speed of sound in the ...
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### Does $Power=F\cdot V$ imply $K.E=mv^2$?

The work done on a body with mass is equal to the constant force applied on the mass, multiplied by the distance over which that force is applied ($W = Fd$). Dividing both sides by the time over which ...
1 vote
50 views

### How can heat generation be $V*I$ when the total power available to a circuit is $V*I$?

If joules law says rate of heat generation in a circuit is $V*I$, but the total power available to a circuit is also $V*I$, then all power in a circuit must go to heat. How can this be possible if a ...
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### What does stand behind the formula: "watt = ampere * volt"?

I know the "watt = ampere * volt" formula, but I don't understand what it means. So, let's start from the beginning. Coulomb answers the question: how many electrons do you have (in a ...
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### Power equation in transmission lines [duplicate]

In transmission lines we increase the power to "reduce energy loss in the form of heat". Can someone explain exactly how and also I understand that we have to keep our power constant ...
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### Calculating the power received by a pixel from a set of rays

I've written a path tracer and am now working on implementing a physically accurate way of simulating the actual sensor response for a given wavelength$^*$, given an exposure time, aperture size, ...
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### Can radio waves with multiple frequencies have the same power?

I was watching data from a spectrum analyzer that shows the frequency of the wave and its power in dBm. I noticed that all frequencies were operating at the same power; however, I don't understand how ...
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### Finding the relation between powers from $V$-$I$ graph

Clearly, resistance of A is greater than that of B. So, my teacher told me, Heat is directly proportional to resistance, hence, the answer is A. However, what I thought was heat is indeed directly ...
1 vote
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### Cause non-linear relation between intensity and photo-current

I wanted to investigate and validate the relationship between intensity and photo-current with a simple experimental setup. I expected a linear relationship based on the photo-diode's datasheet (I've ...
1 vote
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### Power when work is 0

Imagine a rocket of mass m that is at a constant altitude. Gas velocity v. It is necessary to find the power P of the engine. I have a problem: to find the power, you need to divide the work by the ...
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### Understanding the CMB power spectrum 02

I've read many posts, books, articles and so on about the CMB power spectrum (this page for example http://background.uchicago.edu/~whu/intermediate/map5.html) to try to understand it, but I seem to ...
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### Why don't we have underground thermal power plants? [closed]

I learned from wikipedia that for the production of electricity, the temperature of geothermal sources must be at least 150 degrees Celsius. Also wiki says that at a depth of 6 kilometers, the ...
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