Download ppt - Physics Rocks!

Starting at page 180

Review from last unit:
 Electric fields…
▪ Caused by an electric potential difference
▪ Applies a force to a charged particle
▪ Causes (+) to move from high potential to low potential
 If WORK is done to the charged particle…
▪ Then it can be moved from low potential to high
potential
▪ Potential difference (DV) = positive

So…how does this relate to circuits?



In a complete circuit, there must be a source
of potential difference
Electrons within the conductor must have
some agent that applies a net force in order
for them to have net movement in the
conductor
Potential Difference is synonymous with
Voltage


Best conductors = metals, typically
Electrons are free to move among all metal
atoms because of the nature of metallic
bonding—there is a “sea” of electrons

In a battery (cell), when the two terminals are
connected with a conducting wire, there is an
electric field produced within the wire and
battery that applies a force to the electrons,
causing them to move…

The electrons in the battery “drift” towards the
high positive potential end:

Approximate magnitude vdrift= 10-4 m·s-1

The flow of electrons through a conductor as
a result of the application of a potential
difference across the ends of the conductor

Current = rate of flow of charge

Fundamental Units = Ampere

(1 A = 1 C·s-1)
q
I
t

Susie dries her hair in 10.0 minutes. What is
the current flowing through her hair drier if it
takes 6.00 x 103 C of charge to dry it in that
time?
q 6.00 10 C
I 
 10.0 A
t
600.s
3

What state of matter can have an electric
current?
 ANY!!

Charge Carriers = the part of the matter that
allows the charge to be moved through a
potential difference, causing a current
 Solids = free electrons in metals
 Liquids = Ions in molten and aqueous electrolytes
 Gases = electrons and + ions stripped from gas molecules
by large potential differences

a Complete Circuit has:
 A conducting pathway
connecting two ends of …
 A Source of Potential
Difference,
Allowing current to flow
through a…
 Resistive Electrical
Component that consumes
electrical power

Note: DC = direct current
current always flows in the
same direction


Historically, the direction of the flow of
charge carriers was defined to be from
positive to negative
It is now known that current is a flow of
electrons from negative to positive,
however…
 CONVENTIONAL CURRENT STILL IS DRAWN
AND INTERPRETED AS FLOWING FROM
POSITIVE TO NEGATIVE!

A measure of how
easily charge flows
through a material

A Resistor is a
material of significant
resistance that has
been placed in an
electric circuit in order
to control current or
voltage