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Physics Education Technology - University of Colorado, Boulder

Improved HTML5 John Travoltage Simulation

JohnTravoltage Sim

Thank you Dean Baird for your comments regarding the behavior of John Travoltage. We have addressed the issues and the updated John Travoltage is now available at

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Jan 6


2 Comments | Add your comment ↓

  1. Hello PhET Team,

    Thanks for allowing a charge to build up before spontaneous discharge when John’s hand is directed toward the doorknob. A few issues linger.

    The “classic”/Java version allowed for a complete discharge at the greatest hand-to-knob distance, provided that the discharge was initialed at a shorter distance. That is, the spark could be stretched to maximum distance once initiated. This seemed to show the increased conductivity of the ionized channel.

    HTML5 version extinguishes spark before the maximum hand-to-knob distance is achieved.

    The classic version allowed users to establish that discharge channel, extend it to maximum distance, then replenish and maintain a charge on John Travoltage by scraping his foot on the carpet. That is, a full-distance spark could be maintained as long as the user was inclined to work the foot on the carpet.

    The HTML5 version does not seem to allow a spark to be maintained for any significant interval of time. If the foot is rubbed on the carpet while a discharge is in progress, newly addd electrons “lose interest” in the discharge at some point and meander the leg as if nothing were going on at the hand.

    So I am still unable to complete my “Greased Lightning” Lab with the HTML5 version. I appreciate that this is your sim, not mine. And if you intended for the behavior to change between the Java and HTML5 versions, that is your prerogative. If there was a deliberative review of the science and that called for a behavior change at this point, so be it.

    I’m hoping (perhaps unreasonably) that the sim behaviors won’t change between the Classic versions and the HTML5 versions. My thought is that the science was sorted out when the originals were launched/edited, and settled prior to the conversion to HTML5.

    In any case, thanks for the great sims and for allowing them to remain viable as technologies evolve. It is all greatly appreciated.

    • Thanks again for your feedback. This is very helpful in our development of the HTML5 sims. We have forwarded your comments to and our developers and will get back to you soon.

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