Chapter 22 Electric Fields Flashcards Preview

Physics A Level > Chapter 22 Electric Fields > Flashcards

Flashcards in Chapter 22 Electric Fields Deck (24)
Loading flashcards...
1
Q

What is the definition of electric field strength?

A

The electric field at a point in space is the force experienced per unit of positive charge at that point

2
Q

What is the equation for electric field strength?

A
E = F / Q
E = electric field strength
F = force
Q = the amount of positive charge
3
Q

How are electric fiend patterns mapped?

A
  • Arrows on the lines show the direction of the field
  • Electric field lines are always at 90* to the surface of the conductor
  • Equally spaced lines indicate a uniform field
  • Closer electric field lines represent greater electric field strength
4
Q

Is electric field strength a scalar or a vector?

A

vector, it has a direction

5
Q

What is coulombs law?

A

Any two point charges exert an electrostatic force which is proportional to the product of their charges and inversely proportional to the square of their distances

6
Q

What is the equation for coulombs law?

A

F = Qq / 4πε0r^2

7
Q

How can coulombs law be investigated?

A

Two spheres are given each the same charge
One is hung from an insulated rod and the other is held up with an insulating support on top of a balance. They are brought close together a known distance and the change in mass is calculated. And coulombs law equation is used

8
Q

What is the equation for the electric field strength for radial fields?

A

E = Q / 4πε0r^2

9
Q

Why is the equation for a radial field different?

A

Because as you move further away from a radial field the field lines spread out so the force experienced becomes reduced so the charge of the other charge does not need to be factored in.

10
Q

What is ε0?

A

It is the permittivity of free space

11
Q

What is the main difference between gravitational fields and electric fields?

A

Gravitational fields are always attractive

12
Q

What type of field is produced between parallel plates?

A

A uniform field

13
Q

What is the equation for electric fields between two parallel plates?

A
E = V / d 
E = Electric field strength
V = Potential difference
d = Distance between the two parallel plates
14
Q

How is E = V / d derived?

A
W = Fd
VQ = (EQ)d
E = V / d
15
Q

What is the equation for a parallel plate capacitor?

A
C = εA / d
C = Capacitance
ε = The relative permittivity
A = Area of plate
d = Distance between plates
16
Q

What relative permittivity?

A

This is the relative permittivity to ε0.
ε = εr x ε0
εr for a vacuum is defined as 1 because ε0 is for a vacuum

17
Q

What is the equation for the work done on an electron moving through a uniform field?

A

Work done = Ve
V = Voltage
e = Elementary charge

18
Q

What happens when a charged particle enter a uniform field perpendicular to the direction of the electric fields?

A

It moves toward the plate with the oposite charge. It follows a parabolic path

19
Q

How can the path of a charge particle in a uniform field be calculated?

A

The path can be broken down into vertical and horizontal components.

Horizontal has no acceleration so the distance moved(L) = Vt

For vertical we can use F=ma and E = F/Q
Rearranged and combined: a = EQ / m
and v = u + at can also be used
All combined is EQL / mv

20
Q

What is the area under a force distance graph equal to?

A

It is equal to the work done

21
Q

What is the are under a force distance graph equal to for two oposite charges?

A

It is equal to the work done to separate the charges

22
Q

What is electric potential?

A

It is defined as the work done per unit charge in bringing the positive charge from infinity to that point

23
Q

What is electric potential difference?

A

It is the work done per unit of charge between two points around the particle of charge

24
Q

What is the equation for the capacitance of charged spheres?

A

C = 4πε0R