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10.10 Electrical Resistance & Ohm’s Law
Resistance
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Resistance: _________________________________________________
___________________________________________________________
___________________________________________________________
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All substances resist electron flow to some extent.
• Conductors, such as ______________, allow electrons to flow freely through
them and have low resistance values.
• __________________ resist electron flow greatly and have high resistance
values.
Resistance is measured in __________ (Ω) using an ________________
An ohmmeter is a device for measuring ____________________.
When a substance resists the flow of electrons, _____________________
_____________________________________________________________________
_________________________________________________
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Resistance in a Circuit
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A resistor is any material that can slow ______________ flow.
In a light bulb, the filament’s high resistance to the electron’s electrical energy causes it
to _________________ and produce______________.
Resistors and Potential Energy
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Resistors can be used to control electric ________________ or electric
_____________ in a circuit.
In a circuit, electrons have a _____________ potential energy as they enter a resistor
compared to when they leave the resistor because they use up some energy in
passing through the resistor.
Resistance in a wire – water analogy
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_________________________ pipes have ____________ resistance to the flow of
water than pipes with a larger diameter.
The same idea applies to electricity.
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The ___________________________ that you have in a circuit, the more it will
___________________________ at a given voltage.
Larger, shorter wires provide ________________________________ for electrons to
travel.
___________________ and _____________________can also affect resistance.
Ohm`s Law
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Ohm’s law established the relationship between _______________ (V) and
__________________ (I).
Ohm`s law refers to the amount of resistance in a circuit.
The symbol for resistance is called the _________ (Ω) in honour of Georg Ohm’s work
in this field.
According to Ohm`s law, the amount of voltage (or energy) in a circuit is equal to the
current multiplied by the resistance.
Ohm’s law states that, as long as temperature stays the same, ____________
if the resistance of a conductor remains constant, then the current is
______________________________________ to the voltage.
Ohm`s Law and Temperature
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Ohm’s law works for most circuits. However, temperature _______________
resistance. Generally, resistance is _____________when a conductor is
______________. As the temperature increases, resistance increases.
For example, a filament in an incandescent light bulb often has 10 times more
resistance when the bulb is warm.
Calculating Resistance
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Resistance = voltage
current
Sample Problem #1:
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A current of 4.0 A flows through a 40.0 Ω resistor in a circuit. What is the voltage? Use
GRASP and sig. digits.
Sample Problem #2:
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A 30 V battery generates a current through a 15 Ω resistor. How much current does the
battery generate? Use GRASP.
Sample Problem #3:
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An electric stove is connected to a 240-V outlet. If the current flowing through the stove
is 22 A, what is the resistance of the heating element? Use GRASP and sig. digits.