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If there is an AC current in a wire loop, there is a changing B field within the loop.

B field. If there is an AC current in a wire loop, there is a changing B field within the loop. Does this changing B field induce an EMF (voltage) of its own in the loop of wire ? 1) Yes, it must 2) No, it does not. • AC current produces a changing B field.

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If there is an AC current in a wire loop, there is a changing B field within the loop.

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  1. B field If there is an AC current in a wire loop, there is a changing B field within the loop. Does this changing B field induce an EMF (voltage) of its own in the loop of wire? 1) Yes, it must 2) No, it does not. • AC current produces a changing B field. • A changing B field induces an EMF in a loop, even the loop that produces the changing B field • This is called self-inductance

  2. voltage difference large enough for electrons to flow through air If you unplug your computer while it is still on, large voltages may be generated, possibly destroying the CPU chip. Self-Induction in Daily Life When you turn off your toaster by unplugging it  current changes rapidly to zero  rapidly changing B field produced  very large voltage induced in wires of toaster  spark

  3. A solenoid has an inductance of 87.5mH and a resistance of 0.250. Find: The time constant for this circuit: and how long it takes for the current to reach ½ its maximum once connected to a 3volt battery.  = L/R = 87.510-3H/0.250 =0.350 seconds Maximum current is I = 3v/0.250=12 A 6A = 12A(1-e-t/t) ½ = e-t/t ln(½) = -t/0.350sec t = 0.2426sec

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