Coulomb law. Electric Fields of Force. The Force of Electric charges are determined by the type of charge of the objects. unlike charges attract like charges repel A strong charge will attract a weak or neutral charge. Electric Field Patterns.
Describe 3 ways that Charges interact their force lines.
1. Negative and Positive Point Charge: Lines of force radiate from the positive, and inward to the negative
2. Negative and Positive interaction: Forces originate from the Positive and end at the negative using the series of curved lines (attraction)
3. Two Positive charge will deflect force lines away from the charges. (2 Negatives are the same except for direction ( both show repulsion)
The Electric Field is defined as the Force exerted on a tiny positive test charge at that point divided by the magnitude of the test charge:
E is the electric field strength
Fe is the electrostatic force
q is the charge in coulombs
E = Fe
Why is the person in the car protected from the lighting?
The metal “cage” on the inside of the car is uncharged, but the outside surface becomes charged.
Strength of the electric field depends on the density of lines in the region.
E = EA
E = field strength (Vm-1)V = potential difference (V)d = plate separation (m)
Electric Field Strength-Uniform Field
The field strength is the same magnitude and direction at all points in the field
An electron (mass m = 9.11×10-31kg) is accelerated in the uniform field E (E = 1.33×104 N/C) between two parallel charged plates. The separation of the plates is 1.25 cm. The electron is accelerated from rest near the negative plate and passes through a tiny hole in the positive plate, as seen in the figure. With what speed does it leave the hole?
F = qE = ma
a = qE/m
Vf2 = vi2 + 2a(d)
Vf2 = 2ad = 2(qE/m)d
= 2 (1.9 x 10 -19C) (1.33×104 N/C) (1.25m)
= 8.3 x 10 6m/s
m = 9.11×10-31kg
E = 1.33×104 N/C
d = 1.25 cm
k (electrostatic constant =8.99 x 109 N m2/C2)
q (charge in Coulombs)
r ( distance between the charges)
= (8.99 x 109 N m2/C2 ) (6.0 x 10 -6C) (3.0 x 10 -6C)
( 0.030m )2
=(8.99 x 109 N m2/C2 ) (18.0 x 10 -12C)
(9.0 x 10 -4 m2)
= + 1.8 x 10 -8 N