The magnetic field B at the center of a circular coil of wire carrying a current l (as in Fig, 20-9) is
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 made from square copper wire 1.6m on a side.
The power supply produces 120 V at a maximum power output of 4.0kW.
(a) How many turns are needed to run the power supply at maximum power?
(b) what is the magnetic field strength at the center of the coil?
(c) if you use a greater number of turns and this same power supply (so the voltage remains at a120 V), will a greater magnetic field strength result? Explain. |

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