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=O
- B. E < mg / q
- C. E=mg / q
- D. E > mg / q
Explanation
If particle moves with constant velocity, by Newton's laws, net force (ΣF) is zero. ΣF= Electric force + gravitational force = 0Magnitude of electric force = Magnitude of gravitational forceQ x E = m x gE= (mg)/Q
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About Electric Field Intensity
Electric field intensity is the force acting per unit positive test charge, with direction set by the force on that charge. Work includes fields of point charges, vector superposition, field lines and the relation between field and electric potential. Field intensity must be distinguished from electric force and potential.
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