Engineering
Physics
Magnet and Magnetic Dipole
Question

An electron, moving along the x-axis with an initial energy of 100 eV, enters a region of magnetic field B→=(1.5×10−3T) k^ at S (See figure). The field extends between x = 0 and x = 2 cm. The electron is detected at the point Q on a screen placed 8 cm away from the point S. The distance d between P and Q on the screen) si :

(electron’s charge = 1.6 × 10–19C, mass of electron = 9.1 × 10–31 kg)

1.22 cm

11.65 cm

2.25 cm

12.87 cm

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Solution

R=2mkqB

=2×9.1×10−31×100×1.6×10−191.6×10−19×1.5×10−3

R = 2.24 cm

sinθ=xR=22.24=0.89

tanθ=0.890.45≃1.97=h6

h = 11.82 cm

cos θ = 0.45

d = h + 2(1 – 0.45) = 11.82 + 2(1 – 0.45) ≃12.9 cm