Question

You charge a piece of aluminum foil (mass = 6.27 g) by touching it to a charged rod. the charged rod gives the aluminum foil a charge of 12 µc. your professor brings a charged plate over and tells you to put the aluminum foil on top of the plate. to your surprise the aluminum foil hovers motionless in the air above it! calculate the value of the electric field from the charged plate (assume it is a uniform field and the aluminum foil is a point charge).

Answer 1

For this problem, the working equation used is a formula known in electromagnetism. The equation is written below:

E = F/Q
where
E is the strength of electric field
F is the force
Q is the charge

Substituting the values:
E = F/Q = mg/Q = (6.27 g)*(1 kg/1000 g)*(9.81 m/s²)/(12×10⁻⁶ C)
E = 5,125.725 N/C