Download Resistance

• Def : the energy or pushing
force available to move
electrons through a circuit
• Unit: volt (V)
• Symbol: V
• Measured using an
instrument called a voltmeter
V
If
= 1.5 volts
3.0V
?V
Def: difference
between the
charges at the
beginning of a
circuit and at
the end
Charges flow
because of
‘potential
difference’.
3.0 V
3.0 V
0.0 V
•By the time a
charge travels
through a circuit it
will essentially
have lost its
voltage or “push”
• Def: how much the voltage
decreases as it passes through
each resistor on the way back to
the negative end of the battery
• The more light bulbs you
have in a series circuit, the
dimmer they are because
they have to share voltage
• Resistance is the tendency for
materials to oppose the flow of
electricity
Symbol: (R)
Unit: ohm (Ω)
Measured by an ohmmeter
Ω
High resistance = insulators.
Low resistance = conductors.
Anything using electricity is
a resistor!!
Your Turn…
•Find the voltage drop
across the missing
40 bulbs
5
• In a parallel circuit,
the voltage drop
across EACH
resistor is equal to
the total voltage
• Light bulbs wired in
parallel have the
same brightness!
• Def : the rate of “FLOW” of
electrons through a wire
• Unit: Amperes (amp)
• Symbol: I
• It is measured using an
ammeter
A
• Current in a series
circuit is the same
for each resistor
(light bulb).
Current is divided up
between each path; Each
path gets the necessary
number of amps.
TYPES of CURRENT
Direct Current (DC)
Alternating Current (AC)
flows in one direction reverses back and forth
Ex. - Batteries
Ex. – Household current
to Electrical Current
Which of the following do you think
would be most resistant to electrical
Plastic
current?
OR
Insulator
Conductor
Resistance is affected by…
• Length
• The longer the wire, the greater the
resistance
• Diameter
• The smaller the diameter, greater the
resistance
• Material
• Poor conductors have high resistance
• Temperature
• The hotter the wire, the greater the
resistance
Match the word on the left to the
phrase on the right.
Resistance
How Fast?
Current
How much?
Ohms  or R
AMPS (I)
Voltage
Volts (V)
How much
is it slowed
down?