Electric Fields

Question 1

What is the equation for the electric field?

Answer 1

E(r)=lim as q0 goes to of F_0/q0

Question 2

What is the force on a charge in an electric field?

Answer 2

F_0=qoE(r_0)

Question 3

What is the electric field around a point charge at the origin?

Answer 3

E(r)=q/4πϵ0 r̂/r^2

Question 4

What is the direction of the E field?

Answer 4

If q>0 then the E field and unit vector are in the same direction

If q<0 then the E field and unit vector are in the opposite direction

Question 5

Why is the electric field not defined at the point charge?

Answer 5

The E field tends to infinity there

Question 6

How do electric field lines point?

Answer 6

Away from a positive charge and towards a negative charge

Question 7

What is the electric field for a line?

Answer 7

λ =dq/dℓ
dE=λdℓ/4πϵ0 r−r′ /|r− r′|^3
With λ the charge per unit length

Question 8

What is the surface charge density?

Answer 8

The charge per unit area denoted by σ
σ=dq/dS

Question 9

What is the volume charge density?

Answer 9

The charge per unit volume denoted by ρ
ρ=dq/dτ