Upload
tony-pham
View
227
Download
0
Embed Size (px)
Citation preview
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 1/14
Circuit Elements
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 2/14
Objectives
Describe the basic properties of electric current
and solve problems relating current, charge,and time.
Distinguish between the drift speed of a charge
carrier and the average speed of a charge carrier
between collisions.
See how circuits affect our lives everyday.
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 3/14
What Are Circuits Used For?
Every electronic device uses a combination of
circuits!!
Circuits are the pathway for electrical energy to
flow.
Circuits are a closed loop of conductors giving a
clear path for the electrons and therefore
current to flow.
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 4/14
Examples of Circuits
I-Pod Circuit Board
Computer Circuit Board
Cell Phone Circuit Board
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 5/14
Electric Current
Electric Current is the rate at whichelectric charges Pass through a givenarea.
Electric Current is represented by I(Capital i) and it has the unit of Amperesor Amp
I= Q/ t
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 6/14
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 7/14
Drift Speed Drift Speed is the net
speed of a charge carrier
moving in an electric field
Drift speeds are relatively small because of the
many collisions.
If charge moves so slow how do the light turnon almost instantly?
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 8/14
Average speed betweencollisions
Unlike drift speed the speed between collisions
can be in any direction not just in the directionof the electric field.
This is not an average speed but just the speed
between on collision and the next.
The fact that so many collisions happen in such
a short amount of make electricity seem to flowinstantaneously.
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 9/14
Example Problem
How long did it take 6 coulombs of
charge to pass by in order for the
current to have been 9 amperes?
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 10/14
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 11/14
Equation for Resistance
R = V / I this equation isknow as Ohm’s Law
Resistance is Potential
difference divided by the
current.
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 12/14
Ohmic Vs. Non-Ohmic
Ohmic materials follow Ohm’s Law this
means that they have the sameresistance over a wide rang of potential
differences.
Non-Ohmic materials have variableresistance when potential differencechanges.
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 13/14
Resistance Cont’d Resistance depends on the length of the
material, the cross sectional area, thetemperature and the material.
Resistors are objects with knowresistance that are used to control theamount of current flowing through acircuit.
7/31/2019 Circuits Ppt
http://slidepdf.com/reader/full/circuits-ppt 14/14
Checking for Understanding
If a charge is moving at 10 m/s betweencollisions, but the collisions make itchange direction a lot and its average
velocity is 3 m/s. What is the drift speedand what is the speed between collisions?
If the Potential difference in a battery is
8V and the current in the circuit is 2Amps, what is the resistance in thecircuit?