Magnetic Induction Two circular loops of wire are stacked on top of each other a
ID: 2038800 • Letter: M
Question
Magnetic Induction Two circular loops of wire are stacked on top of each other around a common axis as shown. The lower loop carries an electric current which is changing with time. Answer the following questions I increasing I decreasing I increasing I decreasing Note: In cases A and B, the current is flowing in the counterclockwise direction when seen from above, while in cases C and D it is flowing in the clockwise direction above. when seen from 12. Of the four cases labeled A through D, in which case is an induced current flowing in the the upper loop in the clockwise direction when seen from above? Select ALL that apply. If such a current is not flowing in any of the four cases, select E 13. Of the four cases labeled A through D, in which case is an induced current flowing in the the upper loop in the counterclockwise direction when seen from above? Select ALIL that apply. If such a current is not flowing in any of the four cases, select E 14. Of the four cases labeled A through D, in which case is a magnetic force acting on the upper loop in the upward direction? Select ALL that apply. If such a force is not acting in any of the four cases, select E. 15. Of the four cases labeled A through D, in which case is a magnetic force acting on the upper loop in the downward direction? Select ALL that apply. If such a force is not acting in any of the four cases, select E.Explanation / Answer
This is solved using Lenz law, according to which current will be induced in such a way that it opposes its own cause (which produced it).
In first case, I is increasing counter-clockwise, which means its associated magnetic field is also increasing through the upper loop. Now, upper loop will have induced current so as to decrease the magnetic field. It means it will give its magnetic field (upper loop's magnetic field due to induced current) in downward direction, since lower loop magnetic field is upwards (by right hand rule).
Therefore, as seen from above the current will be clockwise in 'A'.
By same reason, in case B, current is decreasing, this time the upper loop will support the magnetic field (so that it does not get decreased), hence it will give its field upward. By right hand rule, the current will be flowing in counter-clockwise direction.
In case C, current is increasing clockwise, or magnetic field is increasing through the upper loop. By right hand rule, this field acts downward. So the upper loop will give its magnetic field upward (so that the field does not get increased). Therefore, the current will be induced counter-clockwise.
In case D, current is decreasing, so does the magnetic field. Therefore, the upper loop will support the magnetic field (so that it does not get decreased). Now, by right hand rule, this field acts downward, hence the upper loop will also give its field downward. By right hand rule, the current will be flowing in clockwise direction.
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