Electric Field
Charge Symbol: q (or Q) Unit: Coulomb, C
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: - 0.00000000000000000016 Coulomb ( = -1.6 x 10-19 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
Electric Field Definition: “It is a region in which a charged object experiences a force”
Demo – Electric Field
Question: How could you increase the force experienced by the charged object in an electric field?
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 ____)
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.
Gravity Field vs. Electric Field
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
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
Work done = Force x Distance How much work is done when a 0.0004 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 0.0004 C, is moved against the electric field by 3 m? (Electric field strength = 1.6 NC-1)
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)
Electric Potential Energy E = electric field strength q = charge d = distance moved inside the field
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.
Worksheet ONE Q1, 2, 3, 4 Worksheet TWO Q1, 2