Question

Now the switch on the electromagnet is reopened. the magnitude of the external magnetic flux through the wire loop ______ (a. increases,

b. decreases,
c. remains constant), and there is _______ (a. zero,
b. a clockwise,
c. a counterclockwise) current induced in the loop (as seen from the left.

Answer 1

When the electromagnet is switched off, the magnetic flux through the loop decreases and induces a clockwise current in the loop, following Lenz's Law.

Step-by-step explanation:

When the switch on the electromagnet is opened, the magnetic flux through the wire loop decreases, and there is a clockwise current induced in the loop (as seen from the left). This is explained by Lenz's Law, which states that an induced current will flow in a direction that opposes the change that produced it. In this scenario, as the external flux decreases due to the switch opening, the induced magnetic field tries to maintain the existing flux through the loop, resulting in a magnetic field that induces a clockwise current in the loop.

Answer 2

Answers:
Blank 1: Option (b) decreases
Blank 2: Option (b) clockwise

Step-by-step explanation:
Blank 1: The answer to the first blank is pretty straightforward that the external magnetic flux through the wire decreases because the electromagnet is reopened. As, after reopening the electromagnet, there will no external magnetic field, hence external magnetic flux would decrease.

Blank 2: According to Lenz’s law, "The current induced in the wire loop opposes the change in the external magnetic flux that caused the current." Therefore, if the external flux has disappeared (as electromagnet is reopened), the induced current should now be opposite to what it was when the field was present. Usually the current is in counterclockwise direction; hence, after electromagnet is reopened, the current would be in opposite direction to counterclockwise direction. Therefore, the correct answer is clockwise direction.