An electric field exists in the space around a charged object. It is defined as the electric force per unit charge. The electric field depends on the charge creating it and the distance from that charge. Electric field lines indicate the direction of the electric field, extending away from positive charges and toward negative charges. The total electric field is the vector sum of the fields from individual charges through superposition.

1. Electric Field

2. Electric Fields
An electric field is said to exist
in the region or space around a
charged object, the source
charge.

3. Electric Fields
Electric field is the Electric force
per unit charge (N/C)
𝐸 =
𝐹
𝑄
Where:
E – Electric Field (N/C)
F – Force (N)
Q – Charge (C)

4. Electric Fields
𝐸 =
𝑘𝑄
𝑟2
Where:
E – Electric Field (N/C)
r – Distance (m)
Q – Charge (C)
Ɛ𝑂 - permitivity of free space-8.854x10−12𝐶2/𝑁𝑚2
K – Proportionality Constant = 9𝑥109𝑁𝑚2/𝐶2

5. Electric Field Lines
- The direction of the fields is defined by the
force on a positive test charge.
A positive test charge is repelled
by a positive charge so the
direction extends away from it.
A positive test charge is attracted by
a negative charge so the direction is
towards a negative point charge.

6. Electric Field Lines
Electric Field lines of two
same point charges.
Electric Field lines of two
opposite point charges.

7. Superposition of Electric Field Lines
𝐸𝑇 = 𝐸1 + 𝐸2 + 𝐸3 + … … 𝐸𝑛
The principle of the superposition of electric
fields states that the electric field of any
combination of charge is the vector sum of the
fields caused by the individual charges.

8. Example
A charge of 6C exerts a force of
2.4𝑥10−4
𝑁 in the right side of a positive
test charge. What is the magnitude and
direction of the electric field at the
location of the test charge?

9. Example
What is the magnitude and direction of
electric field 0f 0.10 m on the left hand
of a -4.2C charge?

10. Example
What is the magnitude and direction of
electric field at a point midway between
two equal and opposite charges of
3.5𝑥10−8
𝐶 which are 5m apart?