Ch. 27 Electromagnetic Induction and Waves - PollEv

B.

The magnetic field points out of the page and the velocity points downward. For rhr, can reverse both directions (pointer/B points into page, thumb/v points up) so that the middle points in the direction of the magnetic force on a positive charge. The force on positive charges points to the left. The force on the negative charges points in the opposite direction.

C. Into the screen

The direction of the magnetic field can be found using curl finger rhr with the given direction of the current (clockwise). The magnetic field (thumb) points into the screen.

Magnetic flux (phi) passing through a loop

A is area of the loop (pi*r² for circular loop)

theta is the angle between the magnetic field and the plane normal to the loop

The current of the wire points left. The magnetic field above the wire goes into the page (curl finger rhr). As the loop approaches the wire, its magnetic flux increases into the page. The induced magnetic field in the loop points out of the page. Using curl finger rhr, the current in the loop is counter clockwise.

The magnetic flux is not changing because the magnetic field around the loop is constant.

Yes, the flux through the loop is changing.

Initial theta = 0 degrees

phi = ABcos(0) = AB → maximum magnetic flux

As the loop rotates, theta increases → the magnetic flux decreases going out of the page.

magnetic flux (phi) = ABcos(theta)

Bwire = muI/2pir → Bwire is proportional to the current

As the current of the wire decreases, its magnetic field to the right of the wire decreases going into the page. The magnetic flux going through the loop decreases going into the page, inducing a magnetic field going into the page. Using curl finger rhr (thumb/field points into page), the current of the loop flows clockwise.

The magnetic flux through the loop is decreasing going into the page. A magnetic field going into the page is induced. The current flows clockwise (curl finger rhr - thumb points into page)

When the switch is closed, the circuit flows counterclockwise (from the positive side of the battery to the negative side). The N pole is above the bottom loop and the S pole is below. The top loop experiences an induced magnetic field in which a N pole is below the loop and a S pole is above the loop. The N pole of the bottom loop repels the N pole of the top loop, which results in an upward force on the top loop.

B.

The magnetic flux decreases going out of the page. The induced magnetic field points out of the page. The current flows counterclockwise