Question

The electric field between the plates of a parallel-plate capacitor is horizontal, uniform, and has a magnitude E. A small object with a charge of -2.12 mu C is attached to the string. The tension in the string is 0.420 N, and the angle it makes with the vertical is 16 \(^\circ\). What is the mass of the object and what is the magnitude of the electric field?

Answer 1

T = tension force = 0.420 N

m = mass of the object = ?

q = magnitude of charge on the object = 2.12 x 10^-6 C

= angle with vertical = 16 deg

E = electric field

Using the equilibrium of force along the vertical direction

T Cos = mg

(0.420) Cos16 = m (9.8)

m = 0.0412 kg

Using equilibrium of force along the horizontal direction

F_e = T Sin

qE = T Sin

(2.12 x 10^-6 ) E = (0.42) Sin16

E = 5.5 x 10⁴ N/C