Physics Electromagnetic Induction UHS 2023
PMDC Verified Question 19 of 69
Velocity selector will select only those charge particle whose velocity is given by:
A
\( V = E/B \)
B
\( V = B/E \)
C
\( V = E \times B \)
D
\( V = 0 \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: \( V = E/B \)
Concept:

A velocity selector utilizes perpendicular electric and magnetic fields to filter charged particles based on speed.

Formula:

$$ F_e = F_b $$

Solution:

  • The electric force (\( F_e = qE \)) and magnetic force (\( F_b = qvB \)) are arranged to oppose each other.


  • For a particle to pass through undeflected, the forces must balance precisely: \( qE = qvB \).


  • Canceling charge (\( q \)) and solving for velocity gives: \( v = \frac{E}{B} \).


Why other options are incorrect:

Option B is the inverted ratio. Option C is mathematically incorrect dimensionally. Option D implies stationary particles, which cannot pass through the apparatus.

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