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9 votes

Does a receiving antenna radiate the power received?

An antenna has an equivalent impedance both in transmit and in receive. If the load in receive mode is matched to that antenna impedance then there is no reflection from that load back out the antenna,...
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4 votes
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Does a receiving antenna radiate the power received?

1.If the incoming E-M wave can induce a voltage won't it accelerate or decelerate the electrons in the wire and doesn't this acceleration cause further radiation (lets call it secondary radiation) of ...
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4 votes

Why is Power = Voltage $\times$ Current?

To get a basic intuition for electrical equations I tend to think of a hydrological analogue. When water is moving through waterways, the difference in elevation corresponds to a potential difference, ...
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3 votes

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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2 votes

Power of a Sr-90 RTG

Strontium-90 produces around 0.95 W/g. However strontium metal is not normally used as a source of heat as it is too chemically reactive. Strontium titanate is often used instead as it is much less ...
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2 votes

Emissivity not accounted for in Equilibrium Temperatures of Planets

I have just been down this rabbit hole, and the formula you're looking for is: $$ T_s^4 = \frac{L(1-\alpha)}{2 \pi \rho D^2(2-\epsilon)} $$ Where: $L$ is stellar luminosity $\alpha$ is your albedo $D$...
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2 votes

Gas stoves are specified in terms of BTUs. Why not units of power?

When used to report powers, BTU actually refers to BTU per hour, which is a proper power unit.
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2 votes

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 ...
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2 votes

Which type of star is most effective for solar power?

If you are using photovoltaic cells then all you care about is the flux of energy above the band gap in your photovoltaic devices. Even for sunlight, about 50% falls below this (wavelengths above ...
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1 vote

Why power of engine must be equal to power of friction?

If the engine produces more power, that has to go somewhere, and in the situation you describe, it will go into kinetic energy, meaning to accelerate the car. If it produces less power, the friction ...
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1 vote
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Gear Ratio And Torque Relationship

The angular acceleration of the smaller one must be 10 times its coupling pair. It is what happens when a car moves from the rest. The motor's RPM grows faster than the wheels' RPM. On the other hand, ...
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1 vote

Which type of star is most effective for solar power?

Only the luminosity of star and the distance to it go into your problem (the power collected would be proportional to the luminosity and inversely proportional to the square of the distance). If you ...
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  • 1,529
1 vote

The Resistance in an electric kettle

The parallel combination of the two Ro resistors is 1 ohm. If there was no resistance R and your kettle were connected to a 120 vac outlet with both switches closed, if would draw 120 Amperes or 14,...
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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 ...
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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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