Download Electric Field Intensity

ELECTRIC FIELD INTENSITY
By:
Engr. Hinesh Kumar
Lecturer
I.B.T, LUMHS
Electric Field Intensity

The strength of the electric field is measured
using a quantity called the electric field
intensity. The greater the electrical field
intensity the stronger the field.

Electric intensity is defined as the force experienced per unit
positive charge at a point placed in the electric field.
E
F
Q
2
Cont…

The electric field is directed from positive
charge and toward the negative charge.

The S.I unit of electric
Newton/Coulomb (N/C).
filed
intensity
is
3
Electric Field Intensity near an
Isolated Point Charge q

Imagine a very small positive charge q˳
placed at a distance r from point charge q˳
q˳
q
r

The magnitude of force on q˳ due to the
charge q is
qq
F
2
4  r
4
Cont…

The final formula of electric field intensity is:
F
q
E

2
q 4  r

The direction of the intensity of electric field
is that the electric force
5
Example # 1

Charges each of +3 μC are placed at three corners of a
square whose diagonal is 6 cm long. Find the field intensity at
D
A
the point of inter section of diagonals.
O
q
E
4  r 2
B
C
Solution:
 The field at O due to charges at A and C mutually cancel
each other being equal and opposite.
 Then the net field is
9
2
2
6
(9 x10 N  m / C )(3x10 )
E
(3x102 ) 2
E  3x107 NC 1
6
Example# 2

Find the electric intensity midway between the charges 1.67*10-7
coulomb and 1.67*10-7 separated by the distance of 60 cm.
7
7
1
.
67

10
C
1.67  10 C
q1

q˳
30 cm
q2
30 cm
Solution
E  E1  E2
E1
E2
E
1 q1
1 q2
E

2
2
4  r1
4  r2
7
Cont…

Since q1=q2 and r1=r2, than formula becomes
1 q1
E  2(
)
2
4  r1
7
E  2(9  10  1.67  10 )
9
E  3.33 NC
4
1
8