Lecture 27- Inductors. Stored energy

# Lecture 27- Inductors. Stored energy - Induction between...

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Lecture 27 Inductors. Stored energy. LR circuits. Induction between two coils Change the current in coil 1 changes the B-flux through coil 2 induces an emf in coil 2 Mutual inductance 2 22 d N dt ε Φ =− 1 1 di M 1 ∝− 21 mutual inductance indicates how large an emf in 2 due to current change in 1 21 1 B i Φ = Of course it works both ways: 2 11 2 12 2 Φ = Mutual inductance depends on the geometry, orientation and materials of the coils. It can be shown that 21 12 MMM =≡ Therefore, we have: 1 2 2 1 12 BB NN ii ΦΦ == Units: SI Henry 1 H = 1 Wb/A

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ACT: Mutual inductance t i 1 ε 2 2 If the current in coil 1 is as shown, which of the graphs gives the correct emf in coil 2? 2 A BC Example: M for two solenoids 02 2 20 2 2 Ni Bn μ == l π Φ= 2 2 12 1 R l μπ = 2 012 1 NN R M l l N 2 turns, length l 1 turns, length l Φ 2 2 11 2 22 () NR ii l l Self-inductance Ideal coil (no resistance) If current through coil changes, flux through coil changes in each loop there is an induced emf loops “in series” emf induced between two ends of coil di/dt di L dt =− The effect is called self-induction Single coil is called an inductor B Φ = ACT: Inductor In the circuit shown, the voltage in the power supply is turned up, so that the current increases. During this operation, which point, y or z , is at a higher potential?
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## This note was uploaded on 09/21/2011 for the course PHYS 222 taught by Professor Johnson during the Spring '07 term at Iowa State.

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Lecture 27- Inductors. Stored energy - Induction between...

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