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Induction coil powering a crt: how does it work?

  1. Oct 13, 2011 #1
    A professor the other day used an induction coil power a crt tube like the one at the link below.


    I understand the general idea of both induction coils and crts, but what confuses me is this: the induction coil he used was didn't have two leads: it was a handheld device plugged into the wall that had a metal point. He brought the tip of the coil near the cathode, and electrons (at least in my understanding) traveled from the tip of the coil to the cathode and then from the cathode to the anode at the other end of the tube. I don't understand how this worked without plugging in the "other end"/ground of the induction coil into the anode. Why does a potential difference between the tip of the induction coil and the ground in the outlet lead to a potential difference between the anode and cathode? Or, phrased a different way, why did the electrons from the cathode travel towards the anode and not in some random other direction?

    Can anyone help me out?

  2. jcsd
  3. Oct 15, 2011 #2
    Capacitance is everywhere, and you especially notice it when the voltage is high and the alternating frequency is high.

    In my time, we used a strange piece of equipment called a phonograph to llisten to music. The voltage from the phonograph usually wasn't very high and if you touched the input to the amplifier, you would be rewarded with a buzzing noise. It was caused by the capacitance between yourself and the house wiring.
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