Chapter 22 Electric Fields

Question 1

what are electric fields due to?

Answer 1

Due to charges

Question 2

what can you model a charged sphere as?

Answer 2

As a point charge at its centre.

Question 3

which direction do electric fields go?

Answer 3

+ to -

Question 4

what is electric field strength? Therefore the equation? Unit?

Answer 4

Force experienced per unit POSITIVE charge at that point.
(Vector quantity)

E = F/Q

NC-1

Question 5

describe Electric Field lines

Answer 5

• equally spaced and parallel
• arrows point to direction of field
• closer lines = greater field strength

Question 6

state Coulomb’s Law

Answer 6

any 2 point charges exert an electrostatic force between them that is directly proportional to product of their charges and inversely proportional to the square of the distances

F (d.p) Qq

F (d.p) 1/r^2

Question 7

combine E = F/Q and F = Qq/4piEr^2

Answer 7

Electric field strength = Q/4piEr^2

Question 8

G.Field vs E.Field

property that creates the field?

Answer 8

G.field - mass

E.field - charge

Question 9

G.Field vs E.Field

Type of field produced?

Answer 9

G - always attractive (direction always towards object)

E -
[+ charge ]
outwards, repulsive field, repels positive charge.

[- charge]
inwards, attractive field, attracts positive charge .

Question 10

G.Field vs E.Field

field strength?

Answer 10

G - g = F/m

E - E = F/q

Question 11

G.Field vs E.Field

Forces between particles?

Answer 11

G - F & Mm , F & 1/r^2

E - F & Qq , F & 1/r^2

Question 12

G.Field vs E.Field

Forces and field strength equations

Answer 12

G - F = -GMm/r^2 , g = -GM/r^2

E - F = Qq/4piEr^2 , E = Q/4piEr^2

Question 13

G.Field vs E.Field

shape of field around a field

Answer 13

G - point MASS produces radial field

E - point CHARGE produces radial field

Question 14

what is a uniform electric field?

Answer 14

A field produced between two parallel oppositely charged plates.
The field is constant

Question 15

Equation for the work done

Answer 15

Work done = force x distance in direction of force

Question 16

what is done when moving a charge in an electric field?

Answer 16

Work is done

Question 17

define the potential difference
and
state the equation

Answer 17

The work done per unit charge in moving a charge from one point to another in a field.

V = W/Q

Question 18

define electric potential

Answer 18

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

Question 19

derive W = EQd

Answer 19

Work done = V x Q = F x D

so = EqD

Question 20

what is electric potential at infinity?

Answer 20

0

Question 21

state equation for electric field strength for parallel plates

Answer 21

E = V/d

so, V = Ed

Question 22

why does an electron have constant acceleration?

Answer 22

Constant electrostatic force due to uniform electric fields between the plates - therefore constant acceleration.

Question 23

what is permittivity

Answer 23

degree to which a medium can resist the flow of electric charge

Question 24

is motion of particles parallel or perpendicular to the field?

Answer 24

parallel

Question 25

in uniform E.F, what is gain in Ek = to ?

Answer 25

work done in moving the charge through the distance between the plates.
where:
W = F x d

Question 26

Describe the particles during horizontal motion

Answer 26

acceleration = 0

time = x/ Vh

Question 27

Describe the particles during vertical motion

Answer 27

u = 0

(F = ma , a = F/m, F= Eq so)
a= Eq/m

Vv = u + at = Vv = at
= Eq/m x X/Vh
= Eqx/VhM