Question

a conduction loop lies flat on a tabletop in a region where the magnetic field vector points straight up. the magnetic field vanishes suddenly. when viewed from above, what is the sense of the induced current in this loop as the field fades?

Answer 1

As the magnetic field pointing straight up vanishes suddenly, an induced counterclockwise (CCW) current is created in the loop, when viewed from above, to oppose the change in magnetic flux.

Step-by-step explanation:

When the magnetic field vanishes suddenly, an induced current will be produced in the conduction loop lying flat on a tabletop, according to Faraday's law of electromagnetic induction. As viewed from above, Lenz's Law states that the direction of this induced current is such that it opposes the change in magnetic flux through the loop. Since the magnetic field vector pointed straight up initially, the sudden absence of this field means the flux is decreasing. To oppose this decrease, the induced magnetic field should point upwards. Using the right-hand rule (RHR-2), if we place our thumb pointing upwards (in the direction we want the magnetic field to be induced), our fingers will wrap around in a counterclockwise (CCW) direction. This is the direction of the induced current when viewed from above.