Oil droplets of mass m and charge q are dropped between two horizontal parallel plates. Air resistance is negligible. The droplets are falling at constant velocity when electric field strength between the plates is E. Which of the following is true?
Correct answer: C. E = mg/q
- A. E-0
- B. E < mg/q
- C. E = mg/q
- D. E > mg/q
Explanation
The forces on the droplet will be due to gravitational pull (related to mass) and due to the applied electric fieldqE will be directed upwards while mg will directed downwards F= ma = qEo -mg = 0 The equation becomes qEo = mg And , Eo = mg/q Therefore only option C is correct
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