# Search results

1. ### Electric field density at the surface of a current carring wire

I've just realized that the same problem comes up with my magnetic field. So. Basically I have no idea what I'm doing and am in need of desperate help.
2. ### Electric field density at the surface of a current carring wire

whoa....okay the equations got screwed up there. Hope you can understand them...B^2 is obviously the one in magnetic energy density, mu sub zero, E^2. Sorry about that folks.
3. ### Electric field density at the surface of a current carring wire

Homework Statement Calculate the magnetic and electric energy densities at the surface of a 3.0 mm diameter copper wire carrying a 15-A current Homework Equations uB=.5\frac{B2}{\mu0} uE=.5\epsilon0E2 R=\rho(L/A) B=(\mu0I)/(2\pir) \rho=1.68 x 10^-8 ohm-meters The Attempt at a...
4. ### Voltage, current, and power wasted

That makes a lot more sense. I was confused as to where to view the potential difference. Thanks for the advice. Incidentally, the 75 kW was a typo, but thanks for pointing it out, too!
5. ### Voltage, current, and power wasted

Homework Statement a power station delivers 750 kW of power at 12,000 V to a factory through wires with total resistance of 3.0 ohms. How much less power is wasted if the electricity is delivered at 50,000 V rather than 12,000 Volts? Homework Equations V=IR P=V^2/R=I^2R The Attempt...