Download Electric Field Lines: Questions

Electric Field Lines
Electric field lines from a point positive charge point outward.
+
Electric field lines from a point negative charge point inward.
In addition:
Closer to the charge where the field is higher, there
is a higher density of lines.
Lines do not cross.
1
Electric Field Lines: Questions
Electric field lines from a point positive charge point outward.
Electric field lines from a point negative charge point inward.
In addition:
Where the field is higher, there is a higher density of lines.
Lines do not cross.
+
Where in this diagram is the field highest ?
Closer to the charge or farther from it ?
2
Electric Field Lines: Questions
Electric field lines from a point positive charge point outward.
Electric field lines from a point negative charge point inward.
In addition:
Where the field is higher, there is a higher density of lines.
Lines do not cross.
C
B
A
Where in this diagram is the field highest ?
Which direction would a positive test charge move?
Which direction would a negative test charge move?
Use points A, B and C as your comparison points.
3
Electric Field Lines: A Dipole
Electric field lines from a point positive charge point outward.
Electric field lines from a point negative charge point inward.
In addition:
Closer to the charge where the field is higher, there
is a higher density of lines.
Lines do not cross.
-
+
In class: join the lines....
4
Electric Field Lines: Two Positive
Charges
Electric field lines from a point positive charge point outward.
Electric field lines from a point negative charge point inward.
In addition:
Closer to the charge where the field is higher, there
is a higher density of lines.
Lines do not cross.
+
+
In class: you cannot join the lines as the come out of both charges
5
Electric Field Lines: A Dipole
Electric field lines from a point positive charge point outward.
Electric field lines from a point negative charge point inward.
In which direction does a positive charged placed at A,B,C,D,E move?
In which direction does a negative charged placed at A,B,C,D,E move?
A
D
-
B
C
+
E
In class: join the lines....
6
Uniform Electric Fields:
Motion of a charge particle
The force on a charged particle q in a uniform electric field
E
Fe =q E
But Newton's Law tells us how a particle with mass m moves under the
influence of an external force (whatever the force is, so it applies to
electric forces too)
=m Fe =q E
a
So:
qE
a =
m
7
Electric Field Lines: Questions
Electric field lines from a point positive charge point outward.
Electric field lines from a point negative charge point inward.
q
E
+
In which direction will the charge move?
8
Uniform Electric Fields:
Motion of a charge particle
qE
i
a =a i=
m
We chose our field along the positive x direction.
We can apply all the kinematics we have learnt.
x
E
q
+
1 2
x f = x iv i t a t
2
and
v f =v ia t
and
v f 2=v i22 a x f x i 9
Uniform Electric Fields:
Motion of a charge particle
Lets assume the particle starts at rest,
And the final position
v i=0
and at
x i=0
x f= x
x
q
E
+
qE
x
v f =2 a x f =2
m
2
and the kinetic energy
1
2
K = m v f =qE x
2
10