Flux Rule- Check that out!
In the given figure, the magnetic field B=1 T points into the page. The dimensions of the loop are as shown in the figure. What is the instantaneous reading of the ammeter (in A) when the switch is thrown from the position, a to b in time t=0.1 s?
Assume that half of the loop is outside the magnetic field.
The answer is 0.
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1 solution
Although there is a flux change through the concerned loop, but there is no force to drive current in the loop. This is actually a flux rule paradox. We often tend to say that whenever there is a change of magnetic flux through a loop, an emf is induced in the loop. However, that flux change should either be due to the motion of the conductor (the driving force here being the Lorentz force) or due to a changing magnetic field (the driving force here being an induced electric field), but it should not be due to switches and the like, as is the case here.
So here no emf is induced and the current flowing is zero.