5.3 Electric Fields

Question 1

Define electric field strength

Answer 1

electric field strength at a point is equal to the force which would be produced on a test charge of 1C at that point

Question 2

Define coulomb’s law

Answer 2

Between every 2 pt charges there exists an electrical force that is directly proportional to the product of the charges and inversely proportional to the square of their separation

Question 3

What is the value of the permittivity of free space

Answer 3

8.85 x 10^-12 C^2N^-1m^-2

Question 4

What are the 3 similarities between electric and magnetic fields

Answer 4

1. electric/grav field around an isolated pt charge decreases in proportion to square of distance 1/r^2
2. both fields around a charged sphere are radial
3. both have fields of infinite range

Question 5

What are the 3 differences between electric and magnetic fields

Answer 5

1. Gravitational field around an isolated pt mass is always radially inwards, electric field is radially outwards if pt mass is positively charged
2. impossible to shield an object from gravitational field, can shield objects from electric fields
3. Gravity acts on masses, electric fields act on charges