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The magnetic field B at the center of a circular coil of wirecarrying a current

ID: 1758705 • Letter: T

Question

The magnetic field B at the center of a circular coil of wirecarrying a current I is

B = 0NI/2r

where N is the number of loops in the coil and r is its radius.Suppose that an electromagnet uses a coil 1.2m in diameter madefrom square copper wire 1.6mm on a side. The power suppply produces120V at a maximum power output of 4kW

a) How many turns are needed to run the power supply at maximumpower?
b) What is the magnetic field strength at the center of thecoil?
c) If you use a greater number of turns in this same power supply(so the voltage remains at 120 V), will a greater magnetic fieldstrength result? Explain.

Explanation / Answer

To calculate the magnetic field at thecenter of the coil, the current must be known, and it canbe

found from the power and the voltagesince PIV