A conducting rod of length \(L\) moves to the right at a constant speed \(v\) along frictionless, parallel horizontal conducting rails connected by a resistor of resistance \(R\). The track and rod system is located in a uniform magnetic field of magnitude \(B\) directed perpendicularly into the plane of the rails, as shown in the diagram. The resistance of the rod and rails is negligible. Which of the following expressions represents the rate at which thermal energy is dissipated in the resistor?