What Determines the Direction of Induced Current in a Parallel Coil Setup?

[chanderjeet]

Homework Statement

P and Q are two coils arranged in parallel to each other and coaxially. Q is connected in series with a cell, a closed switch S and a rheostat. Determine the direction of the current in P when: the switch S is opened.

Homework Equations

Lenz's Law: The direction of the induced emf is such that it tends to oppose the flux change causing it and does oppose it if an induced current flows.

The Attempt at a Solution

A N pole would be present where P is near Q as Q has a N pole near P as the flow of the current in coil Q is anticlockwise. When the switch is opened, the current falls. This is where I'm stuck. Does this mean that the pole in coil P near Q changes? Why? Please explain this

 

[AvroArrow]

further. When the switch S is opened, the current in coil Q will be interrupted. Since the current in coil Q changes, an induced emf is generated in coil P according to Lenz's Law. The direction of this induced emf is such that it opposes the change in flux due to the current in Q. Therefore, the direction of the current in P will be clockwise.

 

[kerimek]

to me.

I would like to clarify that the direction of the induced current in coil P when the switch S is opened depends on the direction of the current flow in coil Q before the switch is opened. If the current flow in coil Q is anticlockwise before the switch is opened, then the induced current in coil P will also be anticlockwise, following Lenz's Law. This is because when the current in coil Q is interrupted by opening the switch, the magnetic field created by the current also decreases, causing an induction of current in coil P in the same direction to oppose this change.

However, if the current flow in coil Q is clockwise before the switch is opened, then the induced current in coil P will be clockwise. This is because when the switch is opened, the magnetic field created by the current in coil Q will collapse, causing an induction of current in coil P in the opposite direction to oppose this change.

In summary, the direction of the induced current in coil P is determined by the direction of the current flow in coil Q before the switch is opened, and it follows Lenz's Law to oppose any change in the magnetic field caused by the interruption of the current in coil Q.