1. Introduction to Electricity
Textbook: ,
Homework: WS

2. Electric Charge
1700s: Benjamin Franklin (American) discovered that there are two types of charges; he gave them the names positive and negative.
Law of Charges:
Opposite charges attract.
Like charges repel.
Charged objects attract neutral objects.
Charging an Object:
Charging by Friction
Charging by Contact
Charging by Induction
Charging by Friction (Demo)
- Some objects hold on to charges better than others (the electrostatic series)
- Ex.
- Diagram of Charging by Friction
- Diagram of Attraction of Neutral Objects
Charging by Contact (Demo)
- Diagram of Charging by Contract
Charging by Induction (Demo)
- Diragram of Charging by Induction

4. Ground: neutralize a charged object by connecting it to the ground

5. 1800s: Charles A. de Coulomb (French) found the magnitude of the force between two charged objects
1900s: Robert A. Millikan (American) performed “Oil Drop Experiment” & found the magnitude of the elementary charge (e)
q = Ne
q = amount of charge [C]
N = # of electrons lost (+ve) or gained (-ve)
e = 1.60 x C
1 C = 6.25 x 1018 electrons ~ 1 mol = 6.02 x 1023 molecules

6. Electric Current
1800s: André Marie Ampère (French) quantified the electric current I (in ampere) through a wire is the total charge Q (in coulombs) flowing through the area A in a time t (in seconds)

7. The Direction of Electric Current
Conventional current or electric current: was defined as positive charges (protons) moving from the positive terminal to the negative terminal of the source
Electron flow: was defined as a flow of negatively charged electrons from the negative terminal to the positive terminal of the source

8. Alternating current (AC)
Direct current (DC)
is in a fixed single direction
doesn’t increase or decrease in magnitude
i.e. batteries, adapters
Alternating current (AC)
Periodically reverses direction in the circuit
the amount of current varies continuously
i.e. a wall socket
Current is measured using an Ammeter

9. A metal-leaf electroscope with 1
A metal-leaf electroscope with 1.25 × 1010 excess positive charges is grounded and discharges completely in 0.50 s. Calculate the average current in the grounding wire.
4.0 × 10^–9 A