Electric Current Chapter 17 in your book

What is Current?  Whenever there is a net flow of charge through a region, current is said to exist rate  Current is the rate at which charge flows through a given area  Whenever there is a net flow of charge through a region, current is said to exist rate  Current is the rate at which charge flows through a given area

 Is current the same as charge?  NO!  Think of Water flowing in a river:  The current in a river is not the water  Current is the flow of the water  In terms of electricity, current is the flow of charge  Current flows opposite the direction of the direction of e - movement e - movement  Is current the same as charge?  NO!  Think of Water flowing in a river:  The current in a river is not the water  Current is the flow of the water  In terms of electricity, current is the flow of charge  Current flows opposite the direction of the direction of e - movement e - movement

Conventional Current

 I = Current  Q = Charge (not heat!)  t = time  I = Current  Q = Charge (not heat!)  t = time ampere SI unit for current is the ampere, A 1A = 1 C/s

Try it, solve for I:  The amount of charge that passes through a fan in 5 s is 30 C. What is the current passing through the fan? I= (30 C) / (5 s) = 6 A

Drift Velocity: The net velocity of the charge carriers The Drift Velocity is relatively small (on the order of cm per min) Why so slow?

What Causes current to flow?  Power sources create a Potential Difference ( +, - terminals on battery)  Charges flow from Higher to Lower electric potential  As long as there is a potential difference a circuit will maintain a current  Power sources create a Potential Difference ( +, - terminals on battery)  Charges flow from Higher to Lower electric potential  As long as there is a potential difference a circuit will maintain a current

AC DC  AC: Alternating Current continuously changes  Motion of charge continuously changes in the forward and reverse directions  AC: Alternating Current continuously changes  Motion of charge continuously changes in the forward and reverse directions  DC: Direct Current one direction  Charge moves continuously in only one direction  DC: Direct Current one direction  Charge moves continuously in only one direction There are two types of current:

Sources:Sources: Batteries: AC or DC? DCDC Generator: AC or DC? BothBoth Chemical Energy to Electrical Energy Mechanical Energy to Electrical Energy

Now Try Practice C in your book – due next class