Electric Potential

Question 1

A conservative force is ….

Answer 1

1) a force with the property that the work done in moving a particle between two points is independent of the path taken
2) electric force is conservative, and thus it as an electric potential energy

Question 2

change of potential energy △U =

Answer 2

△U = Uf - Ui = -W

Question 3

electric potential V at a point is

Answer 3

potential energy per unit charge at a point in an electric field
V = U / q

Question 4

electric potential different △V =

Answer 4

△V = Vf - Vi
= ( Uf / q ) - ( Ui / q )
= △U / q = - W / q
= - ∫ (f to i) E · ds

Question 5

reference potential energy

Answer 5

we set Ui = 0 at infinity as our reference potential energy

V = - W∞ / q

Question 6

the SI unit for potential is

Answer 6

V (volt)

= J / C

Question 7

1 eV

Answer 7

it is a energy
1 eV = e (1V)
= (C) (1 J/C)
= 1 J

Question 8

△K =

the change K in the kinetic energy of the particle

Answer 8

△K = Kf - Ki
= W app + W
= (work done on the particle by an applied force) + (work done on the particle by the electric field)

Question 9

potential due to a point charge

Answer 9

Vf - Vi
= - ∫ ( ∞ to R )E dr
代入E=q/4πε0r²
V = (1/4πε0) (q/r)

Question 10

potential due to a group of point charges

Answer 10

V = Va+Vb+….+Vn

= (1/4πε0) [(qa/ra)+(qb/rb)+….+(qn/rn)]

Question 11

potential due to a electric dipole

Answer 11

V = (1/4πε0) (pcosθ/r²)
#p is the dipole 
#θ is the angle between p and r(-)

Question 12

find potential of continuous charge

Answer 12

by integral of V = (1/4πε0) (q/r)

Question 13

calculating field from potential

Answer 13

Ex = - DV/Dx
Ey = - DV/Dy
Ex = - DV/Dz

Question 14

固定點電荷的電勢能
the electric potential energy of a system of fixed point charges
(potential energy of a system of two point charges)

Answer 14

is equal to the work that must be done by applied force to assemble(組合) the system
U = W = q2 V = (1/4πε0) (q1q2/r)

Question 15

potential energy of a system of three point charges

Answer 15

U = U12 + U13 +U23