1. GOOD
MORNING!!!



2. PHYSICS

3. ANALOGY
The electric field is the space around an
electrical charge
just like
a gravitational field is the space around
a mass.

4. POSITIVE TEST CHARGE
it is a positive charge which is so small that the force
it exerts does not significantly alter the distribution of
the other charges,the ones that cause the field being
measured …
Use sometimes ‘‘POINT CHARGE’.’

5. POINT CHARGE
It is as an idealized charged particles with no real size
or spatial extent.This will allow us todraw electricfield
lines without needing to consider the size of the
charge.

6. ELECTRIC FIELD LINES

7. ELECTRIC FIELD LINES
FOR A POSITIVE POINT CHARGE
The arrows show that a positive test charges would
experievce a force radially OUTWARD FROM THE
POINT CHARGE.All of the begin at the ‘‘same
distence from the point charge.’’
All lines have the same length even though they are
POINTING IN DIFFERENT DIRECTIONS.The
magnitude of the foce is the same at each locations
that are the same distance away from the point
charge.

8. POSITIVE POINT CHARGE

9. ELECTRIC FIELD LINES FOR A NEGATIVE
POINT CHARGES
If the point charge is negative,then the positive test
charge would be attracted towards it.In that case,the
lines of force point radially INWARD TOWARDS THE
NEGATIVE CHARGE.

10. NEGATIVE POINT CHARGE

11. What is the difference?

12. Electric Field Lines of two Same Sign
Charges
The electric field lines point from the charges.There
is an ABSENCE OF LINES in the region between
the charges.This indicates that the FIELD IS
RELATIVELY WEAK BETWEEN THE CHARGES.If
the two charges had been negative,the pattern of
the field lines would be the same as the one for
two positive charges,but the field lines would
point towards the negative charges.

13. Electric Field Lines of two Same Sign Charges

14. Electric Field Lines of two Opposite
Charges
It is also called ELECTRIC DIPOLE,two point charges
that are opposite in sign but equal in magnitude.

15. Electric Field Lines of two Opposite Charges

16. IMPORTANT FEATURES OF
ELECTRIC FIELD LINES
1.Always begin on a positive charge and end on
anegative charge,and do not start or atop the region
between.
2.The number of lines leaving a positive charge or
entering negative charge is proportional to the
magnitude of the charge.
3.‘‘the more lines there are in a given location,the
stronger the field is in that region’’

17. 4.The direction of the electric field at any given points
is the vector drawn tangents to the electric field line
at that point.
‘‘THE LONGER THE ELECTRIC FIELD VECTOR,THE
STRONGER THE ELECTRIC FIELD.’’

18. Conductors and Electric Fields
(under electrostatic conditions)
“The electric field is zero inside a charged
conductor”.
“Excess charge on an isolated conductor resides on
the surface”.
“Excess charge accumulates on sharp points”.
 Electric field lines meet the conductor
perpendicular to the surface of the conductor.

19. Which field is stronger?
A B

20. Electric Field for a Point Charge
Using E=F/qo and Coulomb’s Law prove:
E=k Q
______
r2
where Q is the central charge.

21. Example1
A test charge of +3µC is located 5m to the east of a
-4µC charge.
A) Find the electric force felt by the test charge.
B) Find the electric field at that location.

22. ANSWER :
4.32x10 N, 1.44 x 10 N/C
-3 3
along the –x axis.

23. Examplethe electric field felt by a test charge
Calculate
2
located half way between a charge of +1C and a
charge of -3C, that are 2m apart.

24. ANSWER :
1.8 x 10 N/C
10

25. EXERCISES:
If a test charge is moved to a location three times as far as
its original location, how does the electric field change?
Q equal to -2.0 x 10 to the power of -6 C,R is equal to 20
cm ,k is equal to 9 x 10 to the power of 9 N squared of m
over the squared of coulomb.. Find the E or electric field
strength…

26. THANK YOU
FOR
LISTENING!!
--JOHNNIKKOBABIERASASA