26. W Use Lenz\'s law to answer the following questions con- cerning the directi

Question

26. W Use Lenz's law to answer the following questions con- cerning the direction of induced currents. Express your answers in terms of the letter labels a and bin each part of Figure P23.26. (a) What is the direction of the induced current in the resistor Rin Figure P23.26a when the bar magnet is moved to the left? (b) What is the direction of the current induced in the resistor R immediately after the switch S in Figure P23.26b is closed? (c) What is the direction of the induced current in the resistor R when the current I in Figure P23.26c decreases rapidly to zero Figure P23.26

Explanation / Answer

(a)

When the bar is moved to the left, the magnetic flux associated with the coil decreases and that in turn induces a current in such a way to oppose any decrease in flux. So the current flows from a to b.

(b)

As the switch is closed, the current through the coil increases which in turn increases the flux and flux in tthroug the circuit containing R also increases. So according to lenz's law , a current is induced in the circuit to oppose the increase in flux.So the current through R is from a to b.

(c)

When the current reduces rapidly, the flux associated with the circuit also decreases which in turn induces a current in the circuit to oppose the decrease in flux. So the current through R is from a to b(This curent produces a magnetic field which supports the original field, which was also in the same direction(into the page)).

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