DEMO: Franklin's Bell
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- Опубликовано: 9 июн 2018
- This bell rings when a charged object is brought nearby. It can be understood in terms of the forces on charged conductors.
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You have to move your right hand first and then left
You're a great teacher
This phenomenon is thanks to air being a wonderful dia-electric insulator.
Yes! If it weren't the world would be a bit different.
Beautiful demo but close examination of the action around the 00':07" mark (at 0.25x playback speed) shows the exact opposite motion to that described around the 03'40" timestamp in the theoretical exposition; the pendulum is initially repelled by the charged bell. I wonder if the influence of the negatively-charged Teflon rod on the suspended metallic ball dominates at first as they are closer and this attraction looks like "repulsion" by the RH bell at first. BTW, I'm not questioning basic electrostatics and I have a decent understanding of charge separation and dielectric polarization but just wanted to point out that the initial transient condition is a bit weird!
I think your body became negatively charged also because:
1. You were holding a negatively charged rod.
2. Touching the negatively charged metal a few times.
3. Your movement creating friction between the ground and your shoes which were not good conductors.
As a result, the touching of the metal was ineffective in draining the negative charges anymore and the bells continued to ring.
Good intro-level video, thanks. It just leaves me wanting to know more about why the initial negative charge gets trapped in the bell, but also I want to know about how the original bells worked. Would they have worked best with two grounds? I think they used a non-infinite ground on the leyden jar's exterior so it could hold more charge inside, and that ground doubled as a means to complete the circuit in the bells. Wouldnt this cause a buildup on the outside of the jar? Wouldnt that be dangerous?
The electrons in a conductor move freely in the presence of an electric field, thus they are repelled within the metal rod which is also connected to a bell. This overwhelming charge forces the electrically disconnected neutral ball to move toward the bell...
Potential Difference
Could an eternal circuit be made where the electrons are recycled back to the rod instead of being lost to the ground, thus ringing the bell forever?
No
You have to move your right hand first and then left