1. Electrical Current

2. What do you think of when you hear ‘current’?
Water flowing

3. Electric Current The flow of electrons
The number of charges that pass by a particular point each second
Unit: Amp or Ampere (A)

4. Formula:
I – Current (A)
Q – Charge (C – Coulombs, # of electrons)
t – Time (s)

5. Example:
In a circuit, 2.0 x 1020 electrons pass through a light bulb in 3.3 seconds. If each electron has a charge of x10-19 Coulombs, what current goes through the light bulb?
Ans: I = 9.7 A

6. In a circuit,
Electrons need a push to go through a circuit (this push is commonly called voltage)
The number of electrons pushed (and the speed of these electrons) is current

7. Current Video

8. Two Types of Current Direct Current (DC)
Electrons move in a path without reversing direction
Almost all battery powered devices are DC

9. Charges are forced to reverse directions periodically
Alternating current (AC)
Charges are forced to reverse directions periodically
Easier to produce AC and loses less energy over long distances
Anything that plugs into the wall – most household and industrial appliances

10. Uses Low currents – small portable devices
High currents – heat producing devices

11. Measuring Electric Current
Conventional current (I)
Originally scientists thought positive charges (protons) moved
Later they found out that it was the negative charges (electrons) that actually moved
We still say that current moves from positive to negative
BUT, we acknowledge that what actually happens is electrons move from negative to positive (electron flow – e-)

12. Measure current with an ammeter
Measuring Device
Measure current with an ammeter
Must be in the path of moving charges (in series)
Ammeters must be hooked up in the correct way
Negative to negative, positive to positive

13. Work
Pg 322 # 4-6,7
Pg 323 # 1,3,5