UNIVERSITY OF NEBRASKA-LINCOLN

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Fill in this call number for our section: 6348

6348

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Class Averages(3 exams w/bonus points

and homework quizzes)

average70.4

+ 9590

- 85+ 80

75- 70+ 65

60- 55+ 50

45- 40

These cutoffswill not beraised…youcan use themto determineyour guaranteedlowest grade.

35 40 45 50 55 60 65 70 75 80 85 90 95 100

+-

The switch is closed on this simple circuit of an electromagnet:

time

What might affect how rapidly current reaches its maximum value?

I = V/Rtime switchis closed

Leyden, Holland (1746)Petrus van Musschenbroek

The Leyden Jar

capacitor

- ---- - -

+ ++++ + +

The act of discharging through an inductor creates a

short-lived electromagnet.

But rather than vanishing immediatelythe strength of the electromagnet fades slowly as an induced voltage

tries to sustain the current a little longer!

Discharging through an inductor should slow the process down:

Remember the inductor slows down bothturn-on and the turn-off.

Fully charged capacitor

Current starts

to flow

+ + + +

– – – –

+ +

– –

I

I

I

I

I Maximum

current

Maximumpositive current

Capacitor fully charged

Current flows (opposite direction!)

+ + + +

– – – –

I

+ +

– –

I

+ +

– – I

Current begins to die down

I

I

OscillatorsFully charged capacitor

Energy: all E

+ + + +

– – – –

Capacitor chargedEnergy: all E

Current starts to flowEnergy: some E, some B

Maximum currentEnergy: all B

Current begins to die downinduced

C charges in opposite directionEnergy: some E, some B

Current flows (opposite direction!)

Energy: some E, some B

+ + + +

– – – –

+ +

– –

I

I I

I

+ +

– –

+ +

– –

“Oscillator”

Transmittingantenna

The “tank circuit”the text talks about

tunableoscillator

Receivingantenna

tospeakers

“variablecapacitor”

variable capacitor

inductioncoil

Frequency

A single loop:A small surfacearea capacitor

size ofinductor

size ofcapacitor

1

A specially shaped metal “C”:

smallinductance

coil

tinycapacitor

2.45 GHz

++++- - - -

++++ ++++

++++++++

A microwave’sMAGNETRON

- - - -

- - - -

- - - -- - - -

Recall: the water moleculeis slightly“polar”

it has “sides” that are

oppositely charged

+-

+ ++ +

+ ++ +

- -- ---

tungstenheatingfilament

acceleratedelectronsslam into

the “anode”

+-

+ ++ +

+ ++ +

- -- ---

In which direction are the generated x-rays most likely to be traveling?

UNIVERSITY OF NEBRASKA-LINCOLN

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Fill in this call number for our section: 6348

6348