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Inductor

Inductor. An inductor is a device that temporarily resists change in current flow. induct.html (Please try this applet)

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Page 1: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Inductor

Page 2: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Inductor

• An inductor is a device that temporarily resists change in current flow.

• http://www.falstad.com/circuit/e-induct.html (Please try this applet)

Page 3: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Inductor at t=0

Inductor resists the currently initially.VL jumps to 2.5 V because there is no current in the resistor initially.

Page 4: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Inductor at t>0

1. Inductor slowly gives up its resistance to current2. Current begins to increase3. Voltage across the resistor begins to increase while the voltageacross inductor begins to drop. (Can you explain why?)4. What is limit of the current in the circuit?

Page 5: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

VS transitions to 0V

What happens when VS switches from 2.5 V to 0V?L resists change in current. So initially the resistor will carry0.25 mA of current. Since VS is 0V, VL will be -2.5V.

Page 6: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

The Inductor stops resistant the change in current.The current will slowly decrease to 0.

Page 7: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Plot Inductor Current as a function of time

The current in an inductor can not changeinstantaneously.

Page 8: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Exponential Current Buildup

τ=𝐿 /𝑅

Page 9: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Current versus time

More details in Chapter 7

Page 10: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Exponential decrease of current

τ=𝐿 /𝑅

Page 11: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Current versus time

Page 12: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Why Does an Inductor Oppose Change in Current?

Page 13: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Magnetic Field

Note: The field is stronger closer to the conductor and becomes weakerwith increasing distance from the conductor.

Current

(Magnetic field)

Page 14: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Right-Hand Rule

Thumb: Points in the direction of currentFingers: point in the direction of the magnetic lines of force. Reference: (Floyd, p. 384)

Page 15: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Different Ways of Building Inductors on Silicon

Page 16: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Inductance Calculator

http://www-smirc.stanford.edu/spiralCalc.html

Page 17: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Cumulative magnetic force

Page 18: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Application: Electromagnet

When the coil of wire is connected to a battery, there is current. A magnetic field is established.

Page 19: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Faraday’s observation

• A changing magnetic field can induce a voltage in a conductor.

Page 20: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Faraday’s First Observation

The amount of voltage induced in a coil is directly proportional to the rate of change of the magnetic field with respect to the coil.

Page 21: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Faraday’s second observation

The amount of voltage induced in a coil is directly proportional to the numberof turns of wire in a coil.The induced current generates a voltage across the input resistance of the voltmeter.

Page 22: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Lenz’ law

http://hyperphysics.phy-astr.gsu.edu/HBASE/electric/farlaw.html#c2

When an emf is generated by a change in magnetic flux according to Faraday's Law, the polarity of the induced emf is such that it produces a current whose magnetic field opposes the change which produces it.

Page 23: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Mathematical Definition

Page 24: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Inductors Connected in Series

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Inductors Connected in Parallel

Page 26: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Derivations

• Details shown in class

Page 27: Inductor. An inductor is a device that temporarily resists change in current flow.  induct.html (Please try this applet)

Use an Impedance Analyzer to Measure Inductance