Questions tagged [power]

The time rate of change of energy

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How to convert volt-second data into power-frequency domain?

guys, I am new to physics. Due to my project, I have to utilize my data in the frequency domain. However, my data is in the time domain. So I wanted to ask how I can transform my Volt-time domain data ...
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Why power of engine must be equal to power of friction?

Suppose a car with electrical engine moves uniformly with friction between wheels and the ground (neglect air resistance, energy loss, etc.). So why the car's engine power must be equal to friction's ...
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Gear Ratio And Torque Relationship

suppose a gear teeth ratio of (1:10) >> then it is obvious that the smaller gear will be faster than the larger gear >> And the higher gear has more torque which means a higher ...
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Why is the friction in the motor wrong as an answer to wasted energy in this question?

I do not understand why the answer to part b)ii) cannot be energy lost to friction within the motor as the work done by the motor should be the total work done to move the cyclist and should include a ...
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How to find external surface temperature with unknown heat transfer coefficient?

I am trying to calculate the thickness of insulation required for a certain design. The known properties are the inside temperature, target surface temperature and thermal conductivity. From what I ...
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What happens to electron, when we join two solar panel in parallel

When we add two solar panels in parallel then voltage will remain same but current will increase but what exactly happen to the electrons when current increases but voltage remains the same. Also when ...
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What is the difference between antenna input impedance and its radiation resistance?

I got to know that the input impedance of the halfwave dipole antenna is given as: $Z_{in}$=1/$I_m$* sin($\beta$(H-|Z|)) where $I_m$ is the maximum current on the antenna( when excited with a 1 volt ...
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Which type of star is most effective for solar power?

I'm working on a worldbuilding game, and the subject of stars has come up. Imagine you're a species, chilling in the Goldilocks zone of some alien planet, orbiting an alien star. Your people stumble ...
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The Resistance in an electric kettle [closed]

I have an electric kettle with two parallel heating elements, both with resistance $R_0=2\,\Omega $. Both can be independently shut on and off. There is also another resistor with resistance $R$. Upon ...
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Does a receiving antenna radiate the power received?

Let's consider the case of linear dipole antenna or Hertz dipole. I know that the antenna acts as a transducer and it radiates the E-M waves due to the acceleration and decelaration of the electrons ...
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This question is about motor power requirements

If I have a motor that has a power of 20 kilowatts, does that mean that the motor can produce a torque of 10k newtonmeters at 2 rpm, or analogously a torque of 2 newtonmeters at 10k rpm since the ...
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Gas stoves are specified in terms of BTUs. Why not units of power? [duplicate]

If you go to buy a new gas stove for your kitchen, you will note the main spec of interest is the BTU rating of the burner. Isn't industry making a mistake in using the BTU? The BTU is a unit of ...
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Why is Power = Voltage $\times$ Current?

So P = I*V because V is the amount of energy per coulomb and I is the amount of electrons going past a cross sectional area in one second. So if we do the math, since V = J/C and I = C/sec, if we ...
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Electrical Power and stored power

The simple circuit below, consists of a battery with constant electromotive force (efm), $\epsilon_0$, a capacitor which capacity varies with time $C(t)$ and ,to make it simple, ideal wires (zero ...
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Calculate efficiency from discrete power, time and distance

I have a sequence of points from GPS and OBD for some vehicles. Each point has the instantaneous power of the engine $(P)$, the time elapsed from the last points $(T)$ and the distance traveled from ...
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How will "Fusion Power" deal with it's waste heat?

in application of Fusion power, even if it were doable at present, given the multi-million degree operation, how does such a system dispose of waste heat if plasma is magnetically confined?
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What if a thicker wire is used in the secondary of a step-up transformer?

An n:1 transformer receives a current at its primary and outputs an output voltage V(out)=V(in)*n and an output current I(out)=I(in)/n The output power P(out)=V(out)*I(out)=P(in) as expected by the ...
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High voltage in transmission line [closed]

I'm trying to understand why high voltage is used in transmission but I seem really confused by the explanations I read. Here's what I could make out: $$P_\text{loss} = \dfrac{ΔV^2}{R_t} = \dfrac{(...
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Calculate energy from power time series

I have a time series of power from an EV engine. Something like P = {1000 W, 2000 W, 1000 W, 500 W, 0 W, -500 W}. I also have a timestamp for each point, so I know the time difference between them. I ...
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Intuitive explanation for coefficient in the Larmor formula

So the Larmor formula tells us the total power radiated by an accelerating point charge that doesn't go too fast with respect to the speed of light is $P=\frac{2}{3}\frac{q^2 a^2}{c^3}$ (written in ...
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Can you use the water flow exiting a hydroelectric generator to generate more energy?

In videos of hydroelectric generators I often see that the water that exits a turbine is still moving with significant velocity. Example of a turbine that has exit water flow with significant velocity:...
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Resistance of Electric Bulb Filament and Electric Heater coil

While solving a numerical, I learnt this data: take resistance of bulb filament as $1200 \Omega$ and resistance of electric heater coil as $100 \Omega$. My question is if both bulb and heater are ...
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Wireless Power Transfer in Layered Material

I’m looking to develop a mathematical model for near-field electromagnetic power transfer through layers of human tissue, from an external transmitting antenna to an embedded antenna. Each tissue ...
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Physics basics of junction termination structure (JTE)

I have come across two books that try to explain how a junction termination structure work (low doped implant of the same type as the cathode/anode depending of the substrate type). Both books explain ...
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I have a doubt regarding the supply of power to cities, through transformers

I=Current, V=Potential Difference, R=Resistance, P=Power(just in case if you don't understand wth I am speaking) I understand the contradiction between P=VI and Ohm's Law, and I understand about ...
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Lamp specifications

So when a lamp has a specification of 24 V, 5.0 W, does it mean that it requires at least 5.0 W to work? Can it still consume more power? Or would it then fail? If for example a power supply has ...
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Does a low resistance make it difficult to run a generator?

Imagine I have a simple AC generator. I am providing energy to rotate the coil, which converts this to electrical energy. If I connect the ends to an electrical component such as motor, bulb, the ...
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Is power a cumulative quantity?

Is the power needed to do a particular work cumulative? Like, the power needed to do work W for one second is P, is the power needed to do the same work for 2, 3, 4... seconds equal to 2P, 3P, 4P...?
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How to find peak power at 1550nm using an optical meter?

I have a setup of tunable laser source at 1550nm connected to a spectrometer(Can't publish the name of spectrometer). The spectrometer has a range of 1510-1595 nm. The graph shows wavelength vs ...
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Is power delivered by a force always $F ⋅ V$? [duplicate]

Work done by a force is defined as $F⋅S$, where $F$ is the magnitude of the force and $S$ is the displacement of the object it is acting upon. To find the power delivered by a force we differentiate ...
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Does work only equal the change in energy for non-conservative forces? If so, is power measuring work of non-conservative forces?

I have these formulas: work(net forces) = change in kinetic energy, and then work (non-conservative forces)= change in energy, and power=w/t=change in energy/time. So im confused about what the work ...
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Is the Electrical Power dissipated in a resistor with zero resistance equals to infinity or zero?

Consider a simple circuit consisted of an energy source with constant voltage and a resistor with zero resistance . According to equation for Electrical Power dissipated in a resistor : $P=V^2/R$ ...
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What does it mean to have an over-sized motor?

What does it mean to have an oversized motor? I have read that the Power consumed by a motor under various load conditions is not constant according to the answers to this question (https://...
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Intuition Behind the Maximum Power Transfer Theorem

The Maximum Power Transfer Theorem states that "maximum power transfer occurs when the resistive value of the load is equal in value to that of the voltage sources internal resistance allowing ...
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Reason behind not using $H=V²/R$ for explaining the usage of high voltage in electric transmission lines

The answer to this question says that since there are multiple (3) potential difference across the entire circuit of power lines, the electricity is transmitted at high voltages. Also, they considered ...
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Dimensional Analysis of Force, Work, Energy, and Power

I am working on a review of engineering heat transfer, and would like to include a dimensional analysis section in my notes for the relationship between force, work, energy, and power. This is what I ...
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How to convert (accumulated) $\rm Wh$ to Watt/seconds?

I can measure Wh, but I need to do a graph with Watt/second. How can I achieve that?
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Correct way to estimate trace power spectrum

Assuming that one wants to estimate the trace power spectrum of a field $\vec{B}$ $$\vec{B} = B_{x}\hat{x} + B_{y}\hat{y} +B_{z}\hat{z} $$ Would you have to estimate the PSD of each of the components. ...
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With a properly wired/grounded neutral wire, is it breaking ohm's law?

I have researched and asked some questions around this before, so let me explain. I understand by bonding an Earth ground (literally a green wire to a metal rod in the ground) to the neutral bus bar, ...
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Calculating the wattage of an appliance with radial velocity of domestic electrical meter

There's a heater who's wattage I want to work out. I notice when it is not plugged into the mains socket, the dial on the electric meter for the house spins at x rpm. When it is plugged in, it spins ...
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Power of the car brake system

When I have a car that descends from a stationary position along an inclined plane. If I have that the driver uses the brake system to keep the speed constant, going through 50 m in 10s. Then if I ...
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What is the power of a car rolling at 50 km/h?

I am trying to understand what would be the power difference in watt for making rolling a car of 1000 kg and a bycycle of 80 kg (human + bycycle weight) on a plate road. My car as around 100 ...
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Thermal power station powered by temperature difference between high and low altitude air

Would it be feasible to build a system where warm air from sea level is pumped to the top of a mountain to power a thermal power station? With a lapse rate of ~ 1°C / 100 m there should be plenty of ...
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Does a CPU do work?

This question is simple to the Core (excuse the pun). CPU = Central Processing Unit (for computing) Lots of people including myself say "My CPU is doing a lot of work." But I do not think ...
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Is it accurate to say that a step-up transformer reduces current?

Usually, it is said that step-up transformers are used to transmit power at high voltage and low current, so that $I^{2}R$ losses are minimum. But what does this "low" current actually mean? ...
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A question about power

Pardon me if this is too basic knowledge. It's been a while since my last Physics class in high school so a lot of the knowledge is no longer active in my mind. Here's the question. Say I have a ...
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Mechanical power as $P = F v$

I understand that, in the particular case of a constant force $F$ applied to an object, the speed increases linearly, both the instantaneous power $P$ and the kinetic energy also increase linearly. ...
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Impedance questions for transformers [closed]

For any circuit using AC, we would use impedance to define the overall resistance of the circuit. But to calculate impedance, I have to determine which circuits are in parallel and which circuits are ...
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How long can an industrial generator continue producing power?

I asked this same question over in ElectricalEngineering, and the answers were...less than helpful, let's just say. Plus it got closed for being off-topic. I'm hoping that both of those are resolved ...
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How can you increase power of a light source?

I've heard that red light is dimmer compared to green light emitted with same power and to if you want to have same intensity of light you have to crank up power of red light. From equation for power $...
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