# Tag Info

### Why is Power = Voltage $\times$ Current?

multiplying the rate of flow which is the amount of coulombs passing through a cross sectional area by the potential difference seems very difficult to connect Sorry, but there isn't much more to it ...
• 22.7k

### Why is Power = Voltage $\times$ Current?

Consider a charge $q$ moving with speed $v$. In $t$ seconds it will move a distance $d=vt$, so the current (charge per second passing by that cross section area) is $I = q/t = qv/d$. Electric field ...
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### Why is Power = Voltage $\times$ Current?

Along the lines of the answer by @garyp , it might be good to note that $VI=Fv$ in that answer hints of a "mechanical analogy". Thinking in terms of [generalized-]work (as mechanics or ...
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### Why is Power = Voltage $\times$ Current?

Other answers address why power is given by the product of voltage and current, on grounds of physics. Regardless of the physical meaning we associate with this product, the sum of voltage-current ...
• 7,257

### What exactly is the limiting factor of the efficiency of a heat engine?

What exactly is the limiting factor of the efficiency of a heat engine? The short answer to the title of your post, the limiting factors are the maximum and minimum temperatures between which the ...
• 55.4k
Accepted

### Conservation of energy and work done by a torque

The solid is assumed to be a rigid body. Friction causes rotation and does do rotational work with respect to the center of mass. But, for no slipping of a rigid body, the net work from friction is ...
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### Is work done by torque due to friction in pure rolling?

Which answer is correct? The second answer is correct*. For some reason, friction tends to mentally twist people in knots. It is just an ordinary mechanical force and obeys all of the usual rules ...
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• 5,825
1 vote
Accepted

### Are there two work-energy theorems (rotational and translational) or just a single theorem for both?

Perhaps a derivation. For an extended body, let $\vec R$ describe the motion of the center of mass, and let $\vec r'$ be the position of a point on the rigid body with respect to the center of mass, ...
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1 vote

### Are there two work-energy theorems (rotational and translational) or just a single theorem for both?

What you call the "traditional work-energy theorem" is its application to a particle, or to an extended object where the direction of the net force acting on the object is through its center ...
• 55.4k
1 vote

### Are there two work-energy theorems (rotational and translational) or just a single theorem for both?

To make a clarification, I am unsure about relativistic effects, so I assume we are only considering non-relativistic speeds. To answer your question, it is important to define our translational and ...
1 vote

### Is there a formula of heat that expresses it in microscopic work done?

Your last equation is an expression for the change in internal energy, specifically, the change in the molecular kinteic energy component of internal energy, not heat. There is no such thing as a &...
• 55.4k
1 vote
Accepted

### How to justify that Carnot loop for ideal gas is closed on two sides by adiabatic curves?

The segments are adiabatic (no heat transfer) because the system needs to be brought from temperature of one reservoir to temperature of the other. This can't happen while in contact with any of the ...
• 27.8k
1 vote
Accepted

### Understanding the shape of Carnot loop in the $p$-$V$ plane

It seems that an isobaric path gives the most work per volume. My first observation regarding your drawing of the cycle is that while you are showing heat being added during the isobaric expansion ...
• 55.4k
1 vote

### Understanding the shape of Carnot loop in the $p$-$V$ plane

In carnot engine we care about maximising the efficiency, i.e how much useful work we get out the given heat. Now what is interesting to note is that any reversible engine working between two ...
1 vote

### Why is Power = Voltage $\times$ Current?

"Power" as a concept, on its own, doesn't really make a lot of sense unless you think about what is doing the work. That's because that's what it is: it is the rate of doing work or more ...
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1 vote

### Why is Power = Voltage $\times$ Current?

Let's take water as an analogy. V is the height of fall of the water and I is the volume that falls on the mill wheel. In electricity, V is the potential difference between the source and the sink and ...
• 8,479
1 vote

### Why is Power = Voltage $\times$ Current?

Simplify it. Power is energy in application of delivery to a new or transitioning it's system. The qualities of a engine, motor or conductor dictate how much energy shall be delivered as power in ...
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1 vote

### Why is Power = Voltage $\times$ Current?

The force over the charge of a small volume in an electric field is: $\delta F = \delta q E = \rho A\delta x E$, where $\rho$ is the local density of movable charges and $A$ the wire cross section. If ...
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