Question

As shown in the figure below, a metal rod is pulled to the right at constant speed v, perpendicular to a uniform magnetic field directed out of the screen. The bar rides on frictionless metal rails connected through a resistor forming a complete circuit. The length of the bar between the rails is 5 cm, the magnitude of the magnetic field is 0.4 T, the resistor has a value of 10 Ω, and the speed of the bar to the right is 3 m/s. What is the motional emf across the bar, and which end of the bar is at higher (i.e., positive) potential, the top or the bottom of the bar?

Answer 1

Length of bar

Magnetic field

Speed of bar

The direction of magnetic field is out of the page, and the rod is moving the right with constant speed, there by increasing the outward flux, to oppose the change a current is induced in clockwise direction.

(From Lenz's Law the direction of  current induced is in such a way , that it opposes the magnetic field that produced it.)

That is direction of current is from top to bottom of the bar.

EMF

Direction of current is from top to bottom of bar, so the bottom is at higher potential .