6575 Fill in this call number for our

6575 Fill in this call number for our section: 0 0 9 9 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 0 0 6575 No. SITY OF NEBRASKA-LINCOLN

The switch is closed on this simple circuit of an electromagnet: - + What might affect how rapidly current reaches its maximum value? I = V/R time switch is closed time

Leyden, Holland (1746) Petrus van Musschenbroek

The Leyden Jar capacitor - + + + +

Discharging through an inductor should slow the process down: The act of discharging through an inductor creates a short-lived electromagnet. But rather than vanishing immediately the strength of the electromagnet fades slowly as an induced voltage tries to sustain the current a little longer! Remember the inductor slows down both turn-on and the turn-off.

Fully + + charged capacitor – – I I Current starts to flow + + – – I Maximum positive current I Maximum current I

Current begins to die down I – – I + + Capacitor fully charged –––– I ++++ Current flows (opposite direction!) + + I – – I

Oscillators ++++ Current starts to flow Energy: some E, some B I –– –– Maximum current Energy: all B – – Current begins to die down Þinduced ÞC charges in opposite direction Energy: some E, some B I I + + – – Fully charged capacitor Energy: all E + + I – – Capacitor charged Energy: all E Current flows (opposite direction!) Energy: some E, some B –––– ++++

Transmitting antenna “Oscillator” The “tank circuit” the text talks about

Receiving antenna “variable capacitor” to speakers tunable oscillator

induction coil variable capacitor

Frequency 1 size of inductor capacitor A single loop: A small surface area capacitor A specially shaped metal “C”: small inductance coil tiny + +++ - -capacitor 2. 45 GHz

++ ++ -- -- + + + -- -- ++ A microwave’s MAGNETRON

Recall: the water molecule is slightly “polar” + + + - it has “sides” that are + oppositely charged

tungsten heating filament - + -- --accelerated electrons ++ + + slam into + + the “anode” ++

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