Electrical Current

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

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

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

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 1.60x10-19 Coulombs, what current goes through the light bulb? Ans: I = 9.7 A

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

Current Video

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

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

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

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-)

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

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