#### bob012345

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- A long wire has a current of 1A turned on at time 0. I want to know what the energy in the magnetic field is as a function of time for example, 1ns, 2ns ect.

I want to know the total energy contained in a magnetic field due to a long wire (just consider a 1m segment) as a 1amp current is turned on starting at time zero. I'm assuming zero turn-on time for convenience. At t=0 the cylindrical field is formed and I wish to know the total energy as a function of time, (or equivalent distance ct) where t is in nanoseconds. Is it just the volume integral of the field squared times mu? Thanks.