Two identical circular coils are placed one below the other so that their planes are both horizontal. The top coil is connected to a cell and a switch. The switch is closed and then opened. What is the force between the coils when the switch is closing and when the switch is opening?
Answers
Answer:
Yes, when a current in coil A changes, magnetic field lines linked with coil B also change. Hence, due to change in number of magnetic field lines, there is an induced current in coil B.
Answer:
When closing, there will be a repulsive force. When opening, there will be an attractive force.
Explanation:
First of all the current on the first loop is going clock-wise, thus the magnetic field/force is downwards or towards the second loop.
When the switch is closing, the current flowing through the loop decreases, thus the magnetic field produced decreases. This also means the magnetic flux is decreasing. Using Lenz's law, the induced emf will have to be in such a direction that opposes the change in the source of magnetic flux. Since magnetic flux is decreasing, thus the induced emf will also be downwards. Thus will repel.
While when the switch is opening, the current is increasing and through similar steps explained above the magnetic flux will increase. Again due to Lenz's law it will oppose that increase in magnetic flux by going against it, thus the emf will be upwards. Therefore attractive.