EM problem
Consider a metal wire of length 2m and cross sectional area 2.5E-4 m2, connected to a +/-5V, 120Hz AC power supply. Calculate the magnetic field strength, B, at a distance 2 cm from the wire after 10 seconds. Give your answer to two decimal places.
Resistivity of the wire = 8.5E-8 Ωm.
μ, (permeability of freespace) = 1.26E-6 A/m2.
The answer is 0.03.
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1 solution
R=ρl/A=((8.5E-8)×2)/2.5E-4 = 6.8E-4 Ω
V=vsin(ωt) = 5sin (240π×120) = -1.71V
I=V/R = 1.71/(6.8E-4) =2514.71 A
B=μ,I/2πr= ((12.6E-6)×2514.71)/2π×0.02 = 0.03T to 2d.p.