Electric Fields

Question 1

What produces an electric field?

Answer 1

A charged object

Question 2

What does an electric field do?

Answer 2

Exert a force on charged objects within it

Question 3

What are the 2 most common types of electric fields

Answer 3

Uniform and Radial electric fields

Question 4

General properties of all electric fields:

Answer 4

• Field lines never cross
• Field lines are closer together where the field is stronger
• Field lines are parallel and equidistant for a uniform field
• Spherical or point charges have a radial field
• Field lines are always perpendicular to a surface/object

Question 5

Additional characteristics of electric fields

Answer 5

• They extend to infinity
• Electric field lines go from positive to negative
• They can be attractive or repulsive (gravitational fields are always attractive)

Question 6

Definition of electric field strength

Answer 6

The force experienced per unit (positive) charge at a point in the field

Question 7

Equation of electric field strength

Answer 7

E = F/q

E - E is the electric field strength and has the units NC^-1

F - force experienced
q - the charge of the object in the field

Question 8

Uniform electric fields

Answer 8

The electric field between a pair of parallel plates with a p.d. across them will be uniform
(meaning that the field lines will be parallel and equidistant)

Question 9

Strength of a uniform electric field

Answer 9

The strength of a uniform electric field depends on the p.d. and the separation of the plates as follows:

where E has the units V m^-1 (applies to uniform fields only)