Connect it to a battery

+

• –

• I

• R

• RL Circuits (2)

• Where did the energy in the inductor go?
• How much power was fed to the resistor?

• L

• 

• +

• –

• R

• Integrate to get total energy dissipated

• It went to the resistor

• Powering up an inductor:
• Similar calculation

• L = 4.0 mH

• I

• R

• An inductor with inductance 4.0 mH is discharging through a resistor of resistance R. If, in 1.2 ms, it dissipates half its energy, what is R?

• Sample Problem

• Inductors in Series

• For inductors in series, the inductors have the same current
• Their EMF’s add

• For inductors in parallel, the inductors have the same EMF but different currents

• L1

• L2

• Inductors in Parallel

• L1

• L2

• Parallel and Series - Formulas

	Capacitor	Resistor	Inductor
Series
Parallel
Fundamental Formula

• Materials Inside Inductors

• For capacitors, we gained significantly by putting materials inside
• Can we gain any benefit by putting something in inductors?
• It gives you something to wrap around

• Can materials increase the inductance?
• Most materials have negligible magnetic properties
• A few materials, like iron are ferromagnetic
• They can enhance inductance enormously
• Many inductors (and similar devices, like transformers) have iron cores
• We will ignore this

• Symbol for iron core inductor:
• We won’t make this distinction

• Mutual Inductance

• Consider two solenoids sharing the same volume
• What happens as you close the switch?
• Current flows in one coil
• But Lenz’s Law wants mag. flux constant
• Compensating current flows in other coil
• Allows you to transfer power without circuits being actually connected
• It works even better if source is AC from generator

• 

•