The figures below show two different situations where a current may be induced i

Question

The figures below show two different situations where a current may be induced in a loop according to Faraday's Law, with the direction given by Lenz' Law. The magnetic field strength in Figure 2 is represented by the density of crosses. Select true or false for the current in the loop. The cardinal directions are as defined in the compass rose. Magnet moving East, induced current 'a". Loop moving East, induced current 'b' Loop moving North, induced current 'b". Magnet moving West, induced current 'a". Loop moving South, no induced current. Loop moving West, induced current 'a'. First determine if the flux through the loop is increasing, decreasing or unchanged. (1) If the flux is increasing, then the induced current produces a field that is opposite in direction to the field by the existing magnetic field. (2) If the flux

Explanation / Answer

1. If the magnet recedes from the loop, the induced current should create a "positive" magnetic field (to compensate the decreasing of B).

The answer is FALSE for the statement posted: the induced current should have sense 'b'.

2. TRUE. If the loop moves toward East, B decreases. Thus, the induced current should have the same sense as the initial currenmt in order to compensate the decreasing of B.

3. No changes. The magentic field remains constant by moving B toward N. The current creating an opposing magnetic field to this change has indeed sense 'b'.

4. TRUE. The magnetic field increases by moving the magnet toward West. Thus, the induced current should have such a sense to create a decreasing (opposite) magnetic field.

5. TRUE. See point 3.

6. FALSE. See point 1 (B decreases). It's an identical situation, just the loop is moved in this case. But the Physics situation is the same.

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