The time rate of change of energy

learn more… | top users | synonyms

-2
votes
0answers
24 views

Calculating power [on hold]

I need some help and explanation with solving this question: What is the power required to give a body of mass m a forward acceleration of a when it is moving with velocity v up a frictionless ...
0
votes
1answer
21 views

Finding power with Drag Force equation

The mass of the car is 1500 kg. The shape of the body is such that its aerodynamic drag coefficient is $C_D=0.330$ and the frontal area is $2.50 m^2$. Assuming that the drag force is proportional to ...
-2
votes
1answer
43 views

maximum voltage allowed in the circuit given resistance and power [closed]

I have a circuit established like this: The question is to calculate the maximum voltage the battery is allowed to provide, so each resistor can achieve their maximum power. My attempt: I tried ...
0
votes
2answers
37 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 ...
1
vote
1answer
27 views

Counter rotating propellers: better in same column or staggered?

In an octo-copter design, is it better to put four pairs of counter-rotating props over each other so that each pair works in a column together? Or will you get more power or efficiency from ...
0
votes
1answer
23 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 ...
0
votes
0answers
30 views

What would the graph between P (power) and i (current) look like if the graph between V (potential difference) and i is parabolic?

The answer is same... That us the graph between P and I will also be a parabola.... Similar to the graph between V and I. But how? Can anyone explain through mathematical approach ? I used ...
0
votes
1answer
21 views

Horsepower at certain RPM point without knowing torque?

I want to know the horsepower produced by an engine at certain RPM by knowing another certain RPM point? Let's suppose that an engine produces 200 hp at 4000 RPM, how many horsepower is produced by ...
-1
votes
1answer
31 views

Acceleration Power [closed]

Suppose we have a trolley currently at rest at point A, but the motor switches on, so that it accelerates and reaches point B, at point B, the velocity is 5m/s, Distance of A-B is 10m, mass of the ...
1
vote
0answers
79 views

Power dissipated through resistor in RC circuit with charged Capacitor [closed]

so here's the problem: A simple RC circuit where the capacitor has been charged, and two resistors are in parallel configuration. How does one find the power (as function of time) through any of the ...
4
votes
1answer
76 views

Poynting theorem and entering power

I refer to the time-domain version of the Poyinting theorem in electro-magnetism: $- \displaystyle \oint_S (\mathbf{E} \times \mathbf{H}) \cdot d\mathbf{S} - \int_V \mathbf{E} \cdot \mathbf{J}_i \ dV ...
1
vote
0answers
33 views

Can Somebody give me Questions [closed]

Can someone give me questions on physics because I have my Examination tomorrow Class 9th (CBSE) topic : - Fluids(Density,buoyant Force , Archemedis Principal) , Work Power Energy(Work Basics, ...
0
votes
2answers
87 views

How can you use magnets to rotate a shaft, which in turn powers a generator? [duplicate]

I recently was given the task to create power using magnets, I would think that if I were to put some same poled magnets together, and they were facing the same poled magnets, they would repel and ...
0
votes
0answers
26 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 ...
2
votes
2answers
46 views

Numerical: Work Power Energy [closed]

A particle moves along a straight line. A force acts on the particle which produces a constant power. It starts with initial velocity 3 m/s and after moving a distance 252 m its velocity is 6 m/s. ...
0
votes
0answers
29 views

How to measure power used to sustain something in a (gravitational) field? [duplicate]

I've read this question and answers, but neither of the posts does seem to address my concerns. The problem is as follows: Assuming a device that keeps something in a gravitational field on a ...
0
votes
3answers
93 views

Different formulas for calculating power [duplicate]

$P=IV$, $P=I^2R$, $P=\frac{V^2}{R}$, what are the distinctions between these equations? How do you know which equation to use when?
0
votes
1answer
73 views

Measuring energy when no work is done — comparing push-ups to planks

tl;dr Is there any meaningful (physical) way to compare the energy expended in the exercise of doing $x$ pushups in $t_1$ seconds, vs the exercise of doing the plank for $t_2$ seconds? I'm ...
1
vote
3answers
52 views

Electric Power $P$

In my textbook there are 2 formulas for electric power: $$\begin{array}{cccr} P &=& E/t &\hspace{10pt} (1) \\ P &=& VI. &\hspace{10pt} (2) \end{array}$$ What is the ...
-1
votes
1answer
20 views

Computing power based on weighted averages [closed]

I'm struggling to understand the reason why I'm getting different results with two apparently similar ways to compute the power consumption (over multiple time intervals) of an electrical circuit. ...
0
votes
1answer
44 views

Is it possible to clearly receive weak signal from space?

Imagine there is communication satellite on geostationary orbite. It transmits signal in a defocused beam, "illuminating" whole Earth hemisphere it's floating over. For example, signal is ...
0
votes
1answer
47 views

Is powered delivered to an Incandescent light bulb changing with time? [duplicate]

Initially, when the current starts flowing the temperature of the filament is less and thus resistance is less. So, more current flows through the bulb and the power delivered to the bulb is more. As, ...
1
vote
1answer
44 views

Power of viscous friction on a falling sphere

I have derived a simple model of a rotameter using an homogeneous solid ball in a rigid cone where a fluid flows. I consider 4 forces: Weight, Buyancy, Viscous Friction and Drag. I have written my ...
2
votes
1answer
83 views

Could geothermal energy extraction in Yellowstone significantly diminish the threat of a supervolcano?

I recently read an article about a team in Iceland that had managed to drill directly into magma coming up from the earth's mantle, and then use the resulting bore-hole to generate steam to power ...
-1
votes
3answers
114 views

Why do high current conductors heat up a lot more than high voltage conductors?

120 volts x 20 amps = 2,400 Watts However, if I increased the voltage and lowered the current, you can also use a smaller wire size (more inexpensive), also have less heat and achieve the same watt ...
0
votes
1answer
40 views

What electromagnetic wave produces the strongest electrical current when making contact with an element?

More specifically, what electromagnetic waves can we utilize to generate electrical power and out of those waves, which one would produce the most power? Additionally, which one would be the most ...
1
vote
2answers
146 views

Does gravity exert more “power” when an object is traveling faster?

So, this question arose when I was pondering the meaning of horsepower and torque in cars. I thought of the following question: There is a 1 kilogram weight on planet M. Planet M has no atmosphere ...
4
votes
2answers
157 views

Is a billion volt electrical transmission line possible?

Because $$ P_{loss}=\frac{P^2R}{V^2} $$ in an electrical line where R is total resistance Why not use a 1 billion volt line instead of a 800kv line? Is there a maximum voltage that copper can carry? ...
0
votes
2answers
72 views

How does one estimate the electrical power of a power plant?

I have two related questions that I would like help on: When a power plant creates power like the Hoover Dam, it can provide 2.07 GW of electrical power. My question is what does this mean? I assume ...
1
vote
1answer
463 views

Power dissipated on internal resistance of short-circuited voltage source

Suppose we have a voltage source with an EMF of $\mathcal{E}$ and an internal resistance $R$. If we connect to it a perfect wire with zero resistance, we get a short circuit. The value of the current ...
0
votes
3answers
189 views

Relationship between power and max. speed

I'm talking about the maximum speed if let's say I have a car with the power $P = 1000 \text{W}$ and a force of friction of $5 \mbox{N}$ acting in the opposite direction. After some googling I found ...
0
votes
1answer
138 views

Power loss and Joule's law of heating

I really can't understand the power loss law. If we have a wire carrying a $15\:\mathrm{V}$ and $1\:\mathrm{ A}$ going into an inverter, giving $150\:\mathrm{V}$ and $0.1\:\mathrm{A}$, if we want to ...
2
votes
1answer
483 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
votes
2answers
57 views

Calculating the power of a lightbulb [closed]

How do I calculate the power of a lightbulb? I have values but I don't know the equation to use.
-1
votes
3answers
72 views

Electric Current Power Calculations [closed]

With regards to the equations: $P=VI$ ; $P=V^2/R$ and $P=I^2R$, if you are given $P$, $V$, $I$ and $R$ for a circuit, how do you know which equation to use? Does the use of an equation have to do ...
1
vote
0answers
350 views

Work, Energy, Power, Force question [closed]

Question: 3 boys push a small car 25 m up a hill inclined at 19° to the horizontal. The car has a weight of 860 N and they push it at a steady speed of 0.5 m s-1 against an opposing force of friction ...
1
vote
0answers
269 views

Calculate water use and design parameters for closed loop wet cooling tower

I am looking to estimate water use at a power plant with a closed loop wet cooling tower system. I have done some reading on cooling towers, but am struggling to connect the equations to a final ...
4
votes
5answers
265 views

Intuitively, Why is Power Proportional to $I^2R$

As the resistance of a circuit goes down, the power increases because the current increases, assuming constant voltage. Why is this? I feel like resistance and current are inversely proportional, so ...
0
votes
3answers
3k 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?
0
votes
3answers
109 views

I'm having trouble wrapping my head around force, and thus acceleration, diminishing with a higher velocity when using a constant power

Here is an hypothetical situation I thought about that I don't understand. Let's say I have 2 identical rockets with a fixed power. These rockets start to race in the same direction using the full ...
-4
votes
2answers
318 views

Basic Physics Question [closed]

I'm having a difficult time answering this question. I think I'm just converting the units wrong somewhere: You're the CEO of a courier company, and you decide to select an electric car for your ...
3
votes
2answers
223 views

What does Power really mean?

I've been trying to solve a problem for some time. I have been given conflicting information by both literature, colleagues and people on this very forum. It's a very simple question: What is the ...
2
votes
2answers
168 views

Power as a Function of Distance

I am interested in trying to understand the meaning of the integral of power with respect to distance. In the case of force, we have the two formulae: $\int F \, \operatorname{d}\!t = \Delta p$ and ...
1
vote
0answers
50 views

How power affects heating of a coil

So I am doing a little research on my own about electronic cigarettes. Most Ecig users value high power at a standard current. This means they buy very expensive, high voltage batteries and put high ...
0
votes
2answers
307 views

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

I want to know whether decreasing the weight 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 ...
4
votes
2answers
111 views

Why isn't the product rule used in the definition of mechanical work?

Mechanical power is normally defined as $P = \mathrm{d}W/\mathrm{d}t$, and work is normally defined as $W = \vec F \cdot \vec x$. Today an undergrad pointed out a confusion he had from Griffiths' ...
0
votes
2answers
95 views

Power delivered by centripetal force

Does centripetal acceleration deliver power to the revolving object? What I think: Power is given by F.v Since for a body in circular motion velocity and acceleration are at 90 degrees the power ...
1
vote
0answers
66 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?
11
votes
2answers
182 views

Could a mirror array used for thermal solar power plant double as a telescope at night?

I was looking at the Ivanpah Solar facility and it occurred to me that the large array of mirrors could double as some sort of telescope array at night. The climate in the desert would be ideal for ...
0
votes
0answers
164 views

Power Delivered By An Electromagnetic Wave Versus Power Delivered By A Transmission Line

Background Electromagnetic Waves As I understand it, an electromagnetic wave, like any other wave, is capable of delivering power from a source to a destination. To quantify how much power is ...