1. ELECTRIC FLUX AND
GAUSS’S LAW

2. OBJECTIVES:
 Calculate electric flux
 Use Gauss’s law to infer electric field due to
uniformly distributed charges on long wires,
spheres, and large plates.

3. REVIEW.....
What is ELECTRIC
FIELD?
Electric field is defined as the force
per unit charge at a particular point.

4. REVIEW.....
PROPERTIES OF ELECTRIC
FIELD LINES
 Flux lines generally originate at
positive charges and terminate at
negative charges
The strength of the electric field is
dependent on the number of flux
lines

5. REVIEW.....
PROPERTIES OF ELECTRIC
FIELD LINES
 All the flux lines are parallel to each
other.

6. Let’s check comprehension..
Which is right?
+ -
A B

7. Let’s check comprehension..
Which is stronger?
- -
A B

8. Let’s check comprehension..
Which is right?
- -
A B

10. What is ELECTRIC
FLUX?
The number of field lines passing
through a surface.
ɸ = E.Acosθ
Electric flux
Strength of
the electric
field
Surface
area
Angle
between
the electric
field and
surface
Nm/C
2

13. ELECTRIC
FLUX can
be..
0
POSITIVE
NEGATIVE

14. Let’s
analyze...
NEGATIVE

15. Let’s
analyze...
POSITIVE

16. Let’s
analyze...
0

17. CALCULATING ELECTRIC FLUX
 An electric field of 50.0 N/C makes
an angle of 30.0 with the surface
vector. It has a magnitude of 0.50m.
Find the electric flux that passes
through the surface
2

18. Let’s try!.....
Directions: Solve the following problems systematiclly.
1. Consider a uniform electric field of 300 N/C. What
is the flux of this field through a square of 10 cm
on a side whose plane is parallel to the plane?
2. The square surface measures 3.2 mm on each
side. It is immersed in a uniform electric field with
magnitude E= 1800 N/C. The field lines make an
angle of 35° with a normal to the surface.
Calculate the electric flux through the surface.

19. How does electric
flux related to
GAUSS’S LA

20. What does
the GAUSS’S
LAW?
states?
“The electric flux passing through
any closed surface (known as
Gaussian surface) is equal to
total charge enclosed by the
surface to the permittivity of free
space”
ɸ = q/ɛ
c 0