What is the kinetic energy of an electron that passes undeviated through perpendicular electric and magnetic fields if E = 4.0 kV/m and B = 8.0 mT?
A) 0.65 eV
B) 0.71 eV
C) 0.84 eV
D) 0.54 eV
E) 1.4 eV

Question

Quizplus · Accepted Answer

For an electron to pass undeviated through perpendicular electric (E) and magnetic (B) fields, the electric force (F_e = Ee) must equal the magnetic force (F_m = evB), where e is the charge of an electron (approximately 1.6 x 10^-19 C), and v is the velocity of the electron. Solving for v gives v = E/B. The kinetic energy (KE) of the electron can be calculated using KE = 0.5mv^2, where m is the mass of an electron (approximately 9.11 x 10^-31 kg). Substituting v = E/B into the kinetic energy formula and converting the units appropriately gives the correct kinetic energy value in electronvolts (eV), leading to the correct answer.

What Is the Kinetic Energy of an Electron That Passes