Case : Read the passage and answer the question(s).

Let us consider a straight conductor moving in a uniform and time-independent magnetic field. Figure shows a rectangular conductor PQRS in which the conductor PQ is free to move. The rod PQ is moved towards the left with a constant velocity v as shown in the figure. PQRS forms a closed circuit enclosing an area that changes as PQ moves. The length RQ = x and RS = l and the magnetic flux is Φ_B enclosed by the loop PQRS.

EMF is the negative derivative of flux w.r.t. time. But the expression of EMF so obtained gives a positive value. Why?

x decreases with time.

Since, \(\frac{dx}{dt}\) is negative, it cancels out the inherit negative in the expression for EMF.