A bead of charge +Q and mass m can slide on a smooth rod along y. A plane wave E⃗=E₀ ĵ sin(kx-ωt) is incident. Initially the bead is at rest. Choose the correct statements.
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Question

A bead of charge +Q and mass m can slide on a smooth rod along y. A plane wave E⃗=E₀ ĵ sin(kx−ωt) is incident. Initially the bead is at rest. Choose the correct statements.

G1 Physics · Accepted Answer

At fixed x, m dvᵧ/dt=QE₀sin(kx−ωt). Integration gives the maximum speed change 2QE₀/(mω), so B is true. Since B⃗=(Eᵧ/c)k̂, the magnetic force averaged over one full period is zero, so C is true. Correct: B,C.