# How to find the direction of current in this rotating loop in a magnetic field using right-hand rule for moving charges? So how can you determine the direction of the current here using just the right-hand rule but without using Lenz's law? The textbook says I should use the right-hand rule applied to the velocity of a charge but how does that help find the current? It only finds the resultant magnetic force on the moving charge. In this case, the magnetic flux is increasing, so applying Lenz's law means that the induced current's magnetic field will oppose the the flux which makes sense here with the direction of the current shown. But how can I just use the right-hand rule to find the current direction in this case? That's what my book says. Is there such a way?

The Lorentz force is given by $$\mathbf{F} = q \mathbf{v}\times \mathbf{B}$$ and indicates in which directions the charged particles (electrons here which have negative q) are pushed. If you consider an electron in the upper part of the loop, then we know the velocity direction of this electron and also the magnetic field at the location of the electron. If you then take the cross product of these two quantities, you know the force on the electron (via right-hand rule). The direction of the force will be parallel with the direction of the movement of the electron. The conventional current (movement of positive charges) will be in the direction opposite the flow direction of the electrons. This results in the current indicated on the figure.