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Published byJulianna Maxwell Modified over 9 years ago
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Equivalent Resistance Series and Parallel Circuits
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Two Kinds of circuits
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Circuit Diagrams When drawing pictures of circuits, symbols are used as shorthand instead of pictures of components.
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Circuit Diagrams Instead of a battery, the symbol is used. (Note: sometimes voltage is called emf or potential difference)
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Circuit Diagrams Instead of a resistor, the symbol is used.
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Circuit Diagrams Resistors and batteries will be labeled with their respective values most of the time. 9V 10 Ω
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Practice Draw a series circuit with a 5V battery and two resistors (one 3Ω and the other 5Ω)
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Practice Draw a series circuit with a 5V battery and two resistors (one 3Ω and the other 5Ω) 5V 3 Ω 5 Ω
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Practice Draw a parallel circuit with a 12V battery and two resistors (one 6Ω and the other 2Ω)
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Practice Draw a parallel circuit with a 12V battery and two resistors (one 6Ω and the other 2Ω) 12V 6 Ω2 Ω
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Using Ohm’s Law (V=IR) Ohm’s Law can be applied to A) the WHOLE circuit or B) each RESISTOR separately
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Ohm’s Law- WHOLE Circuit What is R total for the circuit? What is the current? 5V 3 Ω 5 Ω
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Ohm’s Law- WHOLE Circuit R total : I: 5V 3 Ω 5 Ω
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Ohm’s Law- EACH Resistor What is the voltage in each resistor? 5V 3 Ω 5 Ω
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Ohm’s Law- EACH Resistor What do we know about the current in each resistor? 5V 3 Ω 5 Ω
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Ohm’s Law- EACH Resistor What do we know about the current in each resistor? 5V 3 Ω 5 Ω
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Ohm’s Law- EACH Resistor With that in mind we can solve for voltage. 3Ω resistor5Ωresistor 5V 3 Ω 5 Ω
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Ohm’s Law- EACH Resistor With that in mind we can solve for voltage. 3Ω resistor5Ωresistor 5V 3 Ω 5 Ω
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Ohm’s Law- EACH Resistor With that in mind we can solve for voltage. 3Ω resistor5Ωresistor 5V 3 Ω 5 Ω
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Ohm’s Law- EACH Resistor Double check your answer to be sure. 3Ω resistor5Ωresistor 5V 3 Ω 5 Ω
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Summary- SERIES Circuits We can write the ways we used Ohm’s Law as: WholeResistor 1, Resistor 2, Resistor3, … Circuit
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Practice Pg. 650 Practice A
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Ohm’s Law for PARALLEL circuits
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PARALLEL (WHOLE circuit) To apply Ohm’s Law (V=IR) to the WHOLE circuit: V=10V 10V 2 Ω4 Ω
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PARALLEL (WHOLE circuit) To apply Ohm’s Law (V=IR) to the WHOLE circuit: V=10V 10V 2 Ω4 Ω
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PARALLEL (WHOLE circuit) To apply Ohm’s Law (V=IR) to the WHOLE circuit: V=10VR total =1.33ΩI=? 10V 2 Ω4 Ω
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PARALLEL (WHOLE circuit) To apply Ohm’s Law (V=IR) to the WHOLE circuit: V=10VR total =1.33ΩI=? V=IR → 10V=I(1.33Ω) 10V 2 Ω4 Ω
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PARALLEL (WHOLE circuit) To apply Ohm’s Law (V=IR) to the WHOLE circuit: V=10VR total =1.33ΩI=7.51A 10V 2 Ω4 Ω
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PARALLEL (EACH resistor) Now find the CURRENT in each resistor. 10V 2 Ω4 Ω
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PARALLEL (EACH resistor) What do we know about VOLTAGE in a PARALLEL circuit? 10V 2 Ω4 Ω
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PARALLEL (EACH resistor) The VOLTAGE is the same everywhere… 10V 2 Ω4 Ω V= 10Volts everywhere…
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PARALLEL (EACH resistor) Now use V=IR to solve for current at each resistor: 2Ω resistor4Ω resistor 10V 2 Ω4 Ω V= 10V
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PARALLEL (EACH resistor) Total Circuit: V=10VR total =1.33ΩI=7.51A Compare the currents 2Ω resistor4Ω resistor 10V 2 Ω4 Ω V= 10V Equal +
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Summary of Ohm’s Law For PARALLEL circuits: V total =V 1 =V 2 =V 3 =… I total =I 1 +I 2 +I 3 +… 10V 2 Ω4 Ω
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Practice Find A) total resistance in circuit B) current in each resistor 12V 6 Ω2 Ω
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