lecture8

lecture8 - Physics 2102 Physics 2102 Lecture 8 Lecture 8...

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Unformatted text preview: Physics 2102 Physics 2102 Lecture 8 Lecture 8 Capacitors II Capacitors II Physics 2102 Jonathan Dowling Capacitors in parallel and in series Capacitors in parallel and in series • In series : – 1/C eq = 1/C 1 + 1/C 2 – V eq =V 1 + V 2 – Q eq =Q 1= Q 2 C 1 C 2 Q 1 Q 2 C 1 C 2 Q 1 Q 2 • In parallel : – C eq = C 1 + C 2 – V eq =V 1 =V 2 – Q eq =Q 1 +Q 2 C eq Q eq Example 1 Example 1 What is the charge on each capacitor? 10 μ F 30 μ F 20 μ F 120V • Q = CV; V = 120 V • Q 1 = (10 μ F)(120V) = 1200 μ C • Q 2 = (20 μ F)(120V) = 2400 μ C • Q 3 = (30 μ F)(120V) = 3600 μ C Note that: • Total charge (7200 μ C) is shared between the 3 capacitors in the ratio C 1 :C 2 :C 3 — i.e. 1:2:3 Example 2 Example 2 What is the potential difference across each capacitor? 10 μ F 30 μ F 20 μ F 120V • Q = CV; Q is same for all capacitors • Combined C is given by: ) 30 ( 1 ) 20 ( 1 ) 10 ( 1 1 F F F C eq μ μ μ + + = • C eq = 5.46 μ F • Q = CV = (5.46 μ F)(120V) = 655 μ C • V 1 = Q/C 1 = (655 μ C)/(10 μ F) = 65.5 V • V 2 = Q/C 2 = (655...
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This note was uploaded on 11/18/2011 for the course PHYSICS 2102 taught by Professor Dowling during the Fall '10 term at LSU.

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lecture8 - Physics 2102 Physics 2102 Lecture 8 Lecture 8...

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