Transcript Ohm`s Law & Electrical Power

Voltage, Current, Resistance
and Power
Voltage
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Voltage is the ____________________________
through an electric circuit.
Voltage is measured in _____ or ______.
In an electric circuit the voltage may be
provided by a battery, a voltage source or a
potentiometer.
Cell or Battery
Longer Line indicates
positive
Direct Current
Voltage Source
Potentiometer
Electric Current
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Any flow of charge is called an _________________________.
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Current is measured in ________ (_____ or ___).
1 Amp = 1 _____
In electric circuits, we assume it is ________________ flowing
through the circuit (_____________ current).
In reality, it is the ___________________. However in gases
and liquids both positive and negative charges can flow.
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Example 1: Electric Current
A steady current of 4.7 A exists in a wire for 180-s.
a) How much total charge passed by a given point in the circuit during this time?
b) How many electrons was this?
Electric Circuits
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All voltage sources have a ________ “pole” and
a ________ “pole”.
A battery produces current by _________ the
electrons with the negative pole and __________
electrons with the positive pole.
Current will only be produced if there is a _____
path (_______) for the electrons to flow from the
negative pole to the positive pole.
When there is no
closed path, a circuit,
for the electrons to
follow from the
negative pole of the
voltage source to the
positive pole of the
voltage source,
________________
____________!!!!
But once the path is
closed the electrons
are repelled by the
negative pole of the
voltage source and
attracted to the
positive pole of the
voltage source.
Conventional
Current
I
+
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Example 2: Electric Circuit
Which of the set-ups below will cause the bulb to light?
Resistors & Resistance
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A property of all conductors is their ability to _____
the flow of electric current.
This property is called ____________, R.
The units for resistance are ohms, ___.
1 Ω = 1 ______
OR
Resistor
Ohm’s Law
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Georg Simon Ohm discovered that the
resistance, R, was _______ in many conductors.
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This is known as Ohm’s Law.
Materials that obey Ohm’s Law are called
__________.
Materials that don’t obey Ohm’s Law are
called __________.
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Example 3: Ohm's Law
A light bulb has 120-V across it and carries 0.012-A.
a) What is the resistance of the bulb.
b) Find the current through the bulb if the voltage across it is
now 80-V.
c) What voltage would be required to push 1.0-A through the
bulb?
Electrical Power
Electical Power is measured in Watts
If the electrical Device is an Ohmic Resistor:
OR
Example 4: Electrical Power
A light bulb has 110-V across it and a current of 0.5-A through it
a) What is the power of this bulb?
b) What is the resistance of this bulb?