Can Increasing Amperage Generate Arbitrarily Large Power with a Hand Generator?

AI Thread Summary
Using a hand generator, the power produced is determined by the formula P=R(I^2), which implies that increasing resistance can theoretically generate large amounts of power. However, practical limitations arise as higher resistance makes it increasingly difficult to maintain the necessary amperage, thus requiring more physical effort. For instance, producing 200 watts would necessitate supplying at least 200 watts of work to the crank. If resistance is pushed to extreme levels, such as 1MΩ, the resulting voltage could exceed the generator's capacity, leading to potential damage. Ultimately, the power output is constrained by the user's physical strength and the generator's design limits.
tdammon
Messages
1
Reaction score
0
Hi, I am a bit confused about what exactly is being produced when someone uses a hand generator. I know P=R(I^2). Does this mean that if I have a hand crank that can produce 1 amp I can use a 200 ohm resistor and produce 200 watts of power. If this is the case it seems as though producing any amperage can generate an arbitrarily large amount of power.
 
Physics news on Phys.org
tdammon said:
Hi, I am a bit confused about what exactly is being produced when someone uses a hand generator. I know P=R(I^2). Does this mean that if I have a hand crank that can produce 1 amp I can use a 200 ohm resistor and produce 200 watts of power.

Yes

If this is the case it seems as though producing any amperage can generate an arbitrarily large amount of power.

Yeah, if you were strong enough and the generator could handle in, you could produce thousands of horsepower just by turning the crank. Do you reckon you're strong enough? Good luck with that.
 
Sounds about right. But of course to produce that arbitrarily high power will require an even higher amount of power from your hand doing the cranking. You will always be limited by the power of your physique. As the resistance is increased the difficulty in turning the crank and maintaining 1 amp will get harder and harder.
 
You might be able to produce 200 Watts of power - by supplying at least 200 Watts or work to the crank.
Of course, you going to need a good size resistor to dissipate 200 Watts.

Then you figure that with a 1MΩ resistor you'll still be able to force 1 amp through.

If you do, the voltage will be V = RI = 1 million volts. Your hand crank generator probably can't handle that voltage. It will just arc over and start to damage itself.

But you can get one that will hold up. So now we'll choose the resistor.
A common resistor size is 1/4 Watts. For this experiment, that resistor would simply vaporize.
The wattage you are looking to generate is P = R(I^2) = 1 Tera watt.
So you will need to do one of two things, either find a 1 TW resistor or only run the experiment for a few picoseconds.

Now we need to talk about your arm and the mechanical limits of your generator. Are you up to turning that generator with 1TW of power (assuming no Kryptonite).
 
This is from Griffiths' Electrodynamics, 3rd edition, page 352. I am trying to calculate the divergence of the Maxwell stress tensor. The tensor is given as ##T_{ij} =\epsilon_0 (E_iE_j-\frac 1 2 \delta_{ij} E^2)+\frac 1 {\mu_0}(B_iB_j-\frac 1 2 \delta_{ij} B^2)##. To make things easier, I just want to focus on the part with the electrical field, i.e. I want to find the divergence of ##E_{ij}=E_iE_j-\frac 1 2 \delta_{ij}E^2##. In matrix form, this tensor should look like this...
Thread 'Applying the Gauss (1835) formula for force between 2 parallel DC currents'
Please can anyone either:- (1) point me to a derivation of the perpendicular force (Fy) between two very long parallel wires carrying steady currents utilising the formula of Gauss for the force F along the line r between 2 charges? Or alternatively (2) point out where I have gone wrong in my method? I am having problems with calculating the direction and magnitude of the force as expected from modern (Biot-Savart-Maxwell-Lorentz) formula. Here is my method and results so far:- This...
Back
Top