1.The magnetic field at the center of a 0.60-cm-diameter loop is 2.6mT . What is

Question

1.The magnetic field at the center of a 0.60-cm-diameter loop is 2.6mT .

What is the current in the loop?_________A

A long straight wire carries the same current you found in part a. At what distance from the wire is the magnetic field 2.6mT ?_____________________m

2. Two concentric current loops lie in the same plane. The smaller loop has a radius of 3.0 cm and a current of 12 A. The bigger loop has a current of 20 A. The magnetic field at the center of the loops is found to be zero.

What is the radius of the bigger loop?_______________cm

Explanation / Answer

Faraday's law (ref.):
V = N*d(BA)/dt where N = no. of turns, B = magnetic field and A = loop area. Since A is constant, V = NA*dB/dt.
When you have V, you now have to use the resistance-resistivity relationship to calculate loop resistance R. Look up the volume resistivity ? of copper. Calculate the wire cross-section area Aw and length L. R = ?L/Aw. (Be sure that you use length-based units for L and Aw that are compatible with the length-based unit of ?.)
Answers:
A. I = V/R
B. The thermal energy rate = electric power = I^2R

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