8.3 Resistance and the Flow of Electrons
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Transcript of 8.3 Resistance and the Flow of Electrons
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8.3 Resistance and the Flow of Electrons Resistance is the property of any
material that slows down the flow of electrons and transforms electrical energy into other forms of energy.
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8.3 Resistance and the Flow of Electrons A light bulb wire will slow down the
flow of electrons and convert it into light and heat.
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8.3 Resistance and Current Voltage is directly proportional to
current.
If a battery is connected to an electric circuit that has a large resistance, less current will flow than if the same battery is connected to a lower resistance circuit.
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8.3 Ohm’s Law Electrical resistance is the ratio of the voltage
to the current. The unit of measurement for electrical resistance is the ohm .
Ohm’s law is written R = V I
Ohm’s law is more commonly written as :V = IR
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8.3 Ohm’s Law Example 1:The current through a load in a circuit is 1.5A. If the potential difference across the load is 12 V, what is the resistance of the load?
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8.3 Ohm’s Law Example 2:The resistance of a car headlight is 15 . If there is a current of 0.80 A through the headlight, what is the voltage across the headlight?
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8.3 Ohm’s Law Example 3:A 60 V potential difference is measured across a load that has a resistance of 15 . What is the current through this load?
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8.3 Ohm’s Law Converting Prefixes:
milli (m) mA A (÷ 1000)A mA (x 1000)
kilo (k) k (x 1000) k (÷ 1000)
mega (M) MV V (x 1 000 000) V MV (÷ 1 000 000)
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8.3 Ohm’s Law Example 4:A 15 mA current flows through a 400 lamp. What is the voltage across the lamp?
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8.3 Ohm’s Law Example 5:A 12 k load is connected to a 90 V power supply. What is the current thought the load in milliamperes?
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8.3 Determining the Resistance Method 1 Use a voltmeter to measure voltage and
an ammeter to measure current. Using Ohm’s law you can calculate the load’s resistance.
Method 2 Use a multi-meter to measure the
resistance directly.
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8.3 Resistors A resistor is an electrical component
that has a specific resistance. Resistors can be used to control current
or potential difference in a circuit to provide the correct voltage and current to other components of the circuit.
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8.3 Resistance
Resistance is a big loser. When a charge encounters resistance, some of the electrical energy is converted to other forms of energy usually heat.
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8.3 Resistors and Colour Codes
Section 8.3 Quiz