Magnetic Fields and Forces

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Magnetic Fields and Forces

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The University of Vermont
Phys 012 - Elementary Physics
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Lecture 11 Outline of Last Lecture II. Kirchhoff’s Rules a. Junction rule: the total current going into a junction equals the total current out of the junction i. ΣIin = ΣIout ii. Derived from the law of conservation of charge b. Loop rule: the sum of changes in potential around a closed circuit loop is zero i. ΣΔVclosed loop = 0 c. Problem: Find the values for current through the closed circuit below given: ε1 = 10V, ε2 = 14V, R1 = 6Ω, R2 = 4Ω, R3 = 2Ω. i. First, draw currents through this circuit. Direction does not matter at this point in the problem. When you get values for the current, if a value is negative then current flows in the opposite direction as predicted. The magnitude will still be the same. 1. Since ΣIin = ΣIout, for junction A, I1 + I2 = I3. ii. Second, mark each side of every element in the circuit with higher (+) or lower (-) potential. Remember: current flows from high potential to low potential. Physics 012 1st Edition

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