A Conducting Rod Whose Length Is $\ell = 1.60 \mathrm {~m}$

Multiple Choice

A conducting rod whose length is $\ell = 1.60 \mathrm {~m}$ is placed on frictionless $\mathrm { U }$ -shaped metal rails that is connected to a lightbulb having a resistance of $4.00 \Omega$ as shown in the figure. The rails and the rod are in the plane of the page. A constant uniform magnetic field of strength $2.20 \mathrm {~T}$ is applied perpendicular to and out of the paper. An external applied force moves the rod to the right with a constant speed of $6.00 \mathrm {~m} / \mathrm { s }$ . At what rate is energy dissipated in the lightbulb?

A) $21.2 \mathrm {~W}$
B) $112 \mathrm {~W}$
C) $11.5 \mathrm {~W}$
D) $60.0 \mathrm {~W}$
E) $121 \mathrm {~W}$