The time rate of change of energy

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0answers
14 views

In hydroelectric power stations, can i use valves in place of turbines? [on hold]

In hydroelectric power stations, can i use valves in place of turbines? by replacing turbines with valves, we can control flow of water, so we can totally handle hydro electric power stations ...
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1answer
46 views

Quadrupling Power in a Circuit

If I have a heating wire with resistance $R$ to be connected across a constant potential difference $V$, it would seem like cutting the wire into two (thus each having half the resistance) and ...
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1answer
26 views

Sound power radiation of two monopole sources

For a fixed given electrical power to two monopole sources, producing the same frequency. Which mode, either in-phase or out of phase, will radiate the most sound power into the far-field?
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1answer
30 views

Calculating estimated HP from velocity, auto weight, and constant acceleration

I am working on a simulation program that runs theoretical performances of different cars and was wondering if there is a way to estimate the HP at any running RPM? the problem is (and this may be me ...
0
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1answer
79 views

Which thermoelectric effect is better?

I am doing an experiment which requires the thermoelectric effect. I know about the Seebeck and the Peltier effects. Well, from what I have found till now on these topics is that they both can produce ...
4
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3answers
1k views

Why do people with bigger hands/wrists have bigger torque advantages in arm wrestling?

I have arm wrestled people with less strength than me who win simply because they have thicker wrists, or larger hands. It has nary to do with having better technique either, because their wrist size ...
0
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1answer
22 views

Out of phase AC transmission lines in parallel

I've been reading up on power transmission networks and came across this thing. http://en.wikipedia.org/wiki/Quadrature_booster Basically it balances the load between two parallel power lines by ...
1
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2answers
240 views

How much electricity can be produced by my thermoelectric generator?

I am using a thermoelectric cooler from a pc's heatsink to produce electricity. Its size is 30mm by 30mm. I will cool it on one side at -10 degree Celsius and the other at 24 degree Celsius. Can ...
0
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2answers
45 views

Why can't unequal current sources be connected in series?

Imagine two power sources, PS-1 that can supply $5A$ at $100V$,and PS-2 can supply $10A$ at $40V$, due to conservation of charge, and Kirchoff's current law(KCL) this is incorrect, and would lead to ...
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2answers
40 views

Question on power

A wind turbine produces a power $P$ when the wind speed is $v$. Assuming that the efficiency of the turbine is constant, the best estimate for the power produced when the wind speed becomes $2v$ is ...
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0answers
35 views

How big does a natural gas compressor station have to be, so as its possible explosion to produce power equal to that of a nuclear bomb [closed]

I live in Greece and a natural gas compressor station is going to be constructed within a radius of 3km. That got me wondered. Can a possible explosion produce equal power with the little boy, the ...
2
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0answers
127 views

Neutrino power plant

Suppose there is a material that interacts with 50% of high-energy neutrinos. To what temperature such material will heat up naturally here on Earth? What power can be extracted from it?
2
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1answer
42 views

Can a transformer transfer all power?

How can the transformer transfer exact power from primary winding to secondary winding if there are core losses, eddy current losses and hysteresis losses?
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6answers
8k views

Power dissipated in Series versus Parallel

Do two resistors in parallel dissipate more heat per unit time for an applied voltage when compared to two resistors in series?
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1answer
22 views

Power spectral density of noise

My question is regarding power spectral density of white gaussian noise. It is known that the power spectral density of white gaussian noise is $$S_X(f)= \frac{\mathcal{N_0}}{2}$$ My question is does ...
0
votes
1answer
128 views

Do you think it’s possible to make a power plant of the described kind?

We are working on a science project and try to engineer a power plant of a new kind. It is called Air HES (air hydroelectric station). The idea is described on our website. Do you think it is ...
5
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3answers
180 views

Optimal speed for the water wheel

The hydroelectricity plants extract the potential energy of highly deployed massive object (water) as it falls down. Without turbine, all that energy would be converted into speed (kinetic energy) at ...
2
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1answer
61 views

Why high voltage transmission lines?

This is a question which I seem to have tackled multiple times, solved each time after reading a dodgy internet explanation, then partially forgotten about and retackled half a year later. It is time ...
0
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1answer
41 views

If halving signal strength is only a 3db drop, why can't cell phones be much lower powered?

My phone can receive a signal that's -90dBm. That's roughly one-billionth of a milliwatt. Cutting a signal's strength in half only drops the signal by 3dBm. Apart from slightly higher range, is there ...
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2answers
51 views

Power and velocity?

If $P=Fv$, power is constant and the power is the rate of change of kinetic energy, i.e. $P = d(mv^2/2)/dt$, what must $v(t)$ be to satisfy this equation?
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1answer
34 views

Parallel Resistors (special cases formula)

1) A car's rear window defroster uses $n=15$ strips of resistive wire in a parallel arrangement. If the total resistance is 1.4 ohms, what is the resistance of one wire? Solution: I rearranged ...
0
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1answer
32 views

Power - 1/2 Force x velocity? [closed]

A pump, taking water from a large reservoir, is used to spray a jet of water with speed 20m/s. The nozzle of the pipe has radius 0.05m, and is level with the surface of the reservoir (no change in ...
2
votes
1answer
2k views

Finding electric power generated using heat transfer

I'm working through an example I have been given to study. Suppose I have a 2m X 4m photovoltaic panel on my roof that is irradiated with a solar flux of $G_s = 700W/m^2$. Given: $\alpha_s = 0.83$ ...
3
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1answer
169 views

Why is there no upper-bound on power-efficiency of Hydro-turbines?

We have Betz's law, an upper bound on power efficiency, for wind-turbines. But there is no theoretical upper limit on hydro-turbines, Why this is so? Is it mainly due to the incompressibility of ...
3
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4answers
6k views

What is the relationship and difference between BHP and Torque?

I've recently been looking into performance figures for various auto mobiles, and I see the terms BHP and Torque used quite often, but I can't say I really understand the terms, or how they relate to ...
1
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0answers
29 views

What is DX technology and what are the effects on digital cameras?

I am photographing in a high power voltage field in Industry producing aluminium, called DX technology. How do I know if my digital camera will not be affected? At 350kA current my film cameras were ...
-3
votes
1answer
60 views

If a 2,400 lb. car is moving at 1 mile per hour, how much force is required to stop its motion? [closed]

Given that I stand behind or in front of a car and someone will move the car from within at approximately 1 M.P.H., how much force is needed to stop the force driven by the engine to put the car at ...
0
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4answers
28 views

High power short duration from low energy source?

1MW, can 1000Joules source of energy deliver 1M of power in 1 millisecond? $Energy =$ $P$ $x$ $t$ , so does it make sense to have small amounts of energy in large pulses of power? In an extremely ...
4
votes
4answers
8k views

How does power consumption vary with the processor frequency in a typical computer?

I am looking for an estimate on the relationship between the rate of increase of power usage as the frequency of the processor is increased. Any references to findings on this would be helpful.
0
votes
2answers
554 views

Does the mass of a car frame has any effect on its horsepower?

I want to know whether decreasing the mass of the frame of a car will increase its horsepower. From what I understand horsepower is a measure of the car's ability to transport load, and decreasing the ...
0
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1answer
40 views

Making of the electricity

I'm interested if there are actually some new electrons created in the process of Making of the electricity (turbine-generator-electricity)? I guess (flow of the electrons in the wire - electricity) ...
3
votes
1answer
417 views

Power dissipation in circuits:Why is high voltage used in power lines?

I know this question has been asked before, but there is one doubt I still cannot clear. Power dissipation is proportional to $I^2R$. Does this not mean that it is also proportional to $V^2/R$? If ...
0
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1answer
24 views

Does adding water on convex mirror increase its power?

What is the comparison between the power of convex lens in air and in water ? What causes the change in its focal length
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1answer
27 views

Understanding the energy transffered/used from a power source?

A source of power(from a generator,battery,etc...) is used to power a system of any kind. We can calculate the energy used via this formula $E$ = $IV$ x $t$ ? For example, a battery that is connected ...
24
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8answers
5k views

Why don't modern spacecraft use nuclear power?

The Voyager 1 & 2 spacecraft launched in 1977 with Plutonium as their source of electricity. 34 years later they claim these two spacecraft have enough power to last them until at least 2020. That ...
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2answers
33 views

Finding power in series circuit

A resistor of resistance 12 ohms is connected in series with a cell of negligible internal resistance. The power dissipated in the resistor is P. The resistor is replaced with a resistor of resistance ...
0
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1answer
48 views

Getting maximum power/brightness from 5 lightbulbs with different resistances [closed]

Hi I am trying to figure out the best way to arrange 5 lightbulbs to get all of them to have the maximum brightness with a 30V battery. The 5 five lightbulbs have different resistances: 3ohms, 6ohms, ...
0
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2answers
127 views

What's the relation between output voltage and time to boil water given the same kettle?

An electric kettle rated 220V, 2000W needed 10 minutes to boil water when it is half filled with water in Singapore where the output voltage is 220V. Estimate the amount of time needed to do the ...
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2answers
70 views

Why doesn't a resistor dissipate reactive power? [closed]

Is there a (preferably microscopic) explanation for why a resistor does not dissipate reactive power?
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3answers
928 views

How can AC source with different voltage provide same power

As some of us maybe aware, USA mains connection is 110 V while those in Asian countries are 220 V. How is it still possible for the Adapter to provide the necessary power to the device, say a laptop, ...
0
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2answers
27 views

Question about indutive loads in power system [closed]

Our home appliances are mostly resistive loads and the bill we pay for consuming power is actually real power. If we use more inductive loads at our home, will it just cause problems in power factor ...
2
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0answers
41 views

Calculate signal strength received by an Ultrasonic Transducer [closed]

Below is an image showing transducer A transmitting a signal with an amplitude of 3000mV, I am trying to calculate the amplitude of the signal received by transducer B in mV, I understand that there ...
2
votes
2answers
143 views

Power to suspend a mass in air

How much power is needed to suspend a mass in the air? The four parts below deal with the same problem. I post them all here, should there be some subtle things I didn't see. The textbook problem A ...
1
vote
3answers
208 views

How does Ohm's law apply to superconductors?

As radio amateurs we've all learned the various relationships of power, voltage, current and resistance as expressed in Ohm's Law. My question relates to the following simple circuit showing an ideal ...
2
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1answer
40 views

Eddy Currents: Relationships between thickness and deceleration

This is probably a question with a very simple answer, but I want to make sure before I write too much. I'm doing an investigation on Electromagnetic fields, in particular eddy currents and how they ...
2
votes
2answers
110 views

Difference between $I^2R$ and $V^2/R$ and $VI$ for measuring power $P$

We use $I^2R$ or $V^2/R$ or $VI$ for measuring power $P$. Are all of these applicable for all circuits? I have seen in some circuit $V^2/R$ is not equal to $I^2R$. Why is that?
2
votes
3answers
134 views

Will my car consume more if I plug in my laptop?

I drive a Volvo v40 with a 110hp diesel engine. It usually use 4.6L/100km. If I plug my laptop which is 85W, will this change the fuel need? If so, by how much?
0
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1answer
25 views

Why does the power in an inductor equal what it does?

I understand that power is that rate at which work is done and that because of this the power in an inductor is equal to $$P=\frac{d}{dt} \left(\frac12Li^2\right).$$ I also understand that the power ...
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0answers
52 views

Max speed as a function of engine power

My question started out as finding the maximum speed of a go kart, taking into account only the drag forces as force opposing the motor. I've done some investigation to find: $$ F_{drag}=\; ...
1
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1answer
63 views

The inverse square law of sound through solids?

We all know about the inverse square law of sound. In short the power of the wave will get evenly spread on an ever increasing spherical expansion and this will dissipate the power of the wave at a ...