Unit 4: Electric fields

Question 1

What is an electric field

Answer 1

A region in which charged particles experience a force.

Question 2

What is electric field strength and apply it to show an equation for it:

Answer 2

The force experienced per unit positive charge. E = F/Q

Question 3

What are the units for electric field strength:

Answer 3

NC^-1

Question 4

Which direction do field lines go in:

Answer 4

Positive to negative blud

Question 5

What is coulomb’s law:

Answer 5

Force experienced by charges is proportional to the product of the charges and inversely proportional to the distance between them squared.
F = 1/4piE0 * Qq/r^2

Question 6

How can one find field strength at a point in a field:

Answer 6

Combining the two equations F = 1/4piE0 * Qq/r^2 and E = F/Q such that E = 1/4piE0 * Q/r^2

Question 7

What does E = 1/4piE0 * Q/r^2 imply:

Answer 7

Electric field strength is proportional to charge and inversely proportional to distance squared

Question 8

How can one derive E = V/d:

Answer 8

Use W=Fd with F=Eq and V=W/q so that Vq = Eqd, the charges cancel to give V = Ed or E=V/d

Question 9

What variables does capacitance depend upon and what are their relation to capacitance:

Answer 9

Proportional to area of the plates and inversely proportional to the distance.

Question 10

What is the constant of proportionality in capacitance when linked to area and distance:

Answer 10

Permittivity of the insulator between the plates

Question 11

Equation for permittivity of an insulator:

Answer 11

E = Er * E0

Question 12

What is permittivity of a vacuum:

Answer 12

How capable a vacuum is at permitting electric field lines.

Question 13

Define electric potential energy:

Answer 13

The work done to bring the particle from infinity to a separation of ‘r’.

Question 14

How can one find electric potential energy from a force against r diagram:

Answer 14

The area beneath the curve.

Question 15

What is the equation for electric potential energy:

Answer 15

E = Qq/4piE0r

Question 16

Define electric potential:

Answer 16

The work done per unit charge to bring a positive charge to that point from infinity.

Question 17

What’s the key difference between electric potential and electric potential energy and from this derive a basic equation for potential:

Answer 17

Potential is the electric potential energy per unit charge, thus is a property of a field. V = E/q

Question 18

How might one find acceleration for use in suvat equations in electric fields:

Answer 18

a = F/m and F = Eq and E = V/d