Question Detail
Question
What must the charge (sign and magnitude) of a particle of mass 5 g be for it to remain stationary when placed in a downward-directed electric field of magnitude 800 N/C?
Correct Answer
Option B is the correct answer.
Detailed Explanation
For the particle to float, the electric force must point UP and balance the weight: |q|E = mg |q| = mg/E = (0.005)(9.8)/800 = 0.049/800 = 6.125x10-5 C = 61.3 uC. Sign: the field points DOWN, so to get an UPWARD force the charge must be NEGATIVE. Answer: -61.3 uC.
Hint
For the particle to float, the electric force must point UP and balance the weight: |q|E = mg |q| = mg/E = (0.005)(9.8)/800 = 0.049/800 = 6.125x10-5 C = 61.3...