Transcript voltage drop

http://phet.colorado.edu/new/simulations/sims.php?sim
=Ohms_Law
Current
(Amps)
Voltage (Volts)
Resistance
(Ohms or
Ω)
What is the voltage
of this battery?
4.5 V
 Find
the amount of resistance in a
toaster oven that has a voltage of
120 V and has 3 amps of current
running through it.
I
= V/R
3amps = 120V/R
R = 40 Ω
the voltage drop across each
light bulb in the circuit below 2 V
 Find
1Ω
10 V
1Ω
1Ω
1Ω
1Ω
 Voltage
will drop with each resistor.
 The voltage will always drop to 0V in
the end.
2Ω
10 V
2Ω
2Ω
2Ω
2Ω
 You
must ADD the
values of ALL
resistors to find
the total
resistance for the
circuit before you
use Ohm’s Law
 RT = R1 + R2 + R3..
 Find
Your Turn…
the amount of current in the
circuit below I = V/RT I = 1 amp
2Ω
10 V
2Ω
2Ω
2Ω
2Ω
What is
the
current in
each
resistor?
I = V/RT
I=9/3
I = 3 amps
 For
a parallel circuit, voltage drop
over each resistor equals the total
starting voltage
3Ω
12 V
3Ω
3Ω
3Ω
 What
Practice!!
is the voltage drop over
each light bulb? 12 V
 What is the current over each? 4 amps
3Ω
12 V
3Ω
3Ω
3Ω
 In
a parallel circuit, there are
several paths for electrons to
flow
SO……..
 The
current is divided equally
among each branch of a
parallel circuit
Electrical Power
Current (Amps)
P = IV
Power (Watts)
Voltage (Volts)
Electric Companies
 We
pay for
electrical
energy by the
kilowatt-hour
 Remember…..
1 Kilowatt =
1000 watts
 Def:
Devices
that measure
or react to
specific levels
of current
Safety
Examples……
Switches and
Ground Fault
Circuit
Interrupters
(GFCIs)
designed to
stop the flow
of too much
electricity
Examples……
Fuse: contains
a small piece of
metal that melts
if the current
becomes too
high, opening
the circuit
(must be
replaced).
Examples……
Circuit Breaker:
contains a piece of
metal that bends
when it gets hot,
causing a switch
to open the circuit
(can be switched
back on).