Chapter 22 - Electric Fields

Question 1

Electric field strength (E):

Answer 1

The force experienced per unit positive charge at that point

Question 2

Electric field strength formula

Answer 2

E = F/Q

Question 3

Electric field lines

Answer 3

• At right angles to the surface of a conductor
• Equally spaced lines show a uniform field
• Closer lines show a stronger field
• Point from a positive to a negative charge

Question 4

Coulomb’s law

Answer 4

F = Qq/(4πε0r^2)

Question 5

Using Coulomb’s law

Answer 5

Substitute the minus when using negative charges, a negative value is an attractive negative field and a positive is repulsive

Question 6

Electric field strength using Coulomb’s law

Answer 6

E = Q/(4πε0r^2)

Derive by substituting Coulomb’s law into E=F/Q

Question 7

When is the force a maximum

Answer 7

When the separation between the centres is equal to the sum of each radius

Question 8

What do field lines show

Answer 8

The direction of force a positive charge would experience

Question 9

Parallel plates electric field

Answer 9

Produce a uniform force with the same direction at any point

Question 10

εr

Answer 10

The permittivity relative to the permittivity of free space

Question 11

ε

Answer 11

ε0 x εr

Question 12

Electric field strength in terms of potential difference

Answer 12

E =V/d

Question 13

Capacitance in a vacuum

Answer 13

C = ε0A/d

Question 14

Capacitance general formula

Answer 14

C = εA/d

Question 15

Resultant electric potential

Answer 15

Sum the electric potential of each

Question 16

Moving non-parallel to an electric field

Answer 16

Resolve perpendicular and parallel
Perpendicular velocity is constant
Parallel component changes due to the electric field

Question 17

Electric potential definition

Answer 17

The work done to bring a charge from infinity to a point in an electric field per unit positive charge.

Question 18

Electric potential equation

Answer 18

V = Q/4πε0r

Question 19

Electric potential energy in terms of electric potential

Answer 19

E = Vq

Question 20

Electric potential energy

Answer 20

E = Qq/4πε0r

Question 21

Investigating Coulomb’s law

Answer 21

Take a top-pan balance with a positive charge on a support and another above on a rod
Set the balance to 0 before the second charge is added and find the force using mg as the top charge is added

Question 22

Field lines with a positive sphere and a negative plate

Answer 22

Curve from the sphere to the plate, must be perpendicular to the surface of the sphere and the plate