1. Electric Field

2. Charge
Symbol: q (or Q)
Unit: Coulomb, C

3. 6.25 x 1018 electrons = -1 C ( = -1.6 x 10-19 C)
Electrons are negatively charged.
In fact, the charge of a single electron is:
Coulomb
( = -1.6 x C)
An object has +1 coulomb of charge if it loses 6,250,000,000,000,000,000 electrons!
6.25 x 1018 electrons = -1 C

4. Electric Field Definition:
“It is a region in which a charged object experiences a force”

5. Demo – Electric Field

6. Question:
How could you increase the force experienced by the charged object in an electric field?

7. F = E q The magnitude of the force depends on two things:
the charge of the object (q)
the electric field strength (E)
F = E q
E = electric field strength (measured in ___)
q = charge (measured in ____)

8. Example
An object with a small charge, 2 x 10-9 C, is left in an electric field. The electric field strength is 7.5 x 104 NC-1.
Calculate the size of the force that the object experiences.

9. Gravity Field vs. Electric Field

10. Gravity Field = It is a region in which an object with mass experiences a force
Electric Field = It is a region in which a charged object experiences a force

11. F = mg F = Eq In a Gravity Field: In an Electric Field:
The force (F) experienced by the object depends on:
The mass of the object (m)
The strength of the field (g)
F = mg
In an Electric Field:
The charge of the object (q)
The strength of the field (E)
F = Eq

12. Work done = Force x Distance
How much work is done when a kg object is lifted by 3 m on the Moon?
(The moon’s gravity = 1.6 ms-2)
How much work is done when an object with a charge of C, is moved against the electric field by 3 m?
(Electric field strength = 1.6 NC-1)

13. Work done = Force x Distance
Work done in gravity field:
W = F x d
= mg x h
= mgh (= gravitational potential energy)
Work done in electric field:
= Eq x d
= Eqd (= electric potential energy)

15. Electric Potential Energy
E = electric field strength
q = charge
d = distance moved inside the field

16. EXAMPLE
A charged object (q = 15 C) was moved in an electric field (0.003 NC-1) by a distance of 0.2 m, against the force.
Did the object gain or lose electric potential energy?
Calculate the size of the electric potential energy.

17. Worksheet ONE Q1, 2, 3, 4
Worksheet TWO Q1, 2