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Restless Electrons

Restless Electrons. Mechanisms for Transfer of Charge. How do objects gain “static” charge?. Friction Rubbing two electrically neutral objects together can charge both objects – both gain OPPOSITE charge Conduction

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Restless Electrons

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  1. Restless Electrons Mechanisms for Transfer of Charge

  2. How do objects gain “static” charge? • Friction • Rubbing two electrically neutral objects together can charge both objects – both gain OPPOSITE charge • Conduction • Charged object TOUCHES another object – electrons jump from one to the other in an attempt to EQUALIZE the charge on both objects • Induction • Charged object comes near another object WITHOUT TOUCHING – causes it to POLARIZE

  3. Why is it the electrons that are usually transferred during charging? • Electrons are much smaller (2000 X) than the protons so they are easier to move. • Electrons are located outside the nucleus of the atom in the electron cloud. This makes them loosely connected to the atom and easier to remove.

  4. Conductive Properties of Solids special metal alloys metals wood silicon rubber pure water sea water SUPER CONDUCTORS SEMI INSULATORS CONDUCTORS CONDUCTORS Conductors allow charge to flow through them easily high conductivity Insulators inhibit charge flow high resistivity

  5. Friction This works best when two INSULATORS are rubbed against one another

  6. John Travoltage Balloons Charging By Friction

  7. ConductionNegative To Neutral - - Excess electrons exert repulsive forces on one another, causing them to move apart as much as possible BOTH now have the same charge!

  8. Electrons in the neutral object experience an attractive force. They neutralize some of the positive charge, leaving both with a lack of electrons ConductionPositive To Neutral + + BOTH now have the same charge!

  9. Excess electrons exert force against nearby electrons in the neutral object InductionNegative To Neutral - Polarization + -

  10. Electrons in the neutral object experience an attractive force, which pulls them closer to the charged object InductionPositive To Neutral + Polarization - + Balloons Again

  11. Permanently Charging Two Spheres by Induction

  12. Grounding Since the Earth is so large it can equalize charges from other objects very easily The Earth can equalize charge by: absorbing excess electrons from negatively charged objects giving free electrons to positively charged objects In either case, grounding a charged object makes it neutral One symbol that is often used to show that something is grounded is:

  13. Charging One Sphere By Induction with Grounding

  14. Electroscope An electroscope is a device that detects CHARGE - - - - - When the scope is CHARGED, the LEAVES at the bottom will REPEL one another The charged LEAVES exert force on one another, forcing them apart - -

  15. Electroscope – negative cond. Step 5 Scope is once again neutral – excess electrons are gone Step 3 Scope is now negatively charged Step 4 Scope is grounded allowing electrons to escape Step 1 Negative rod touches neutral scope Step 2 Electrons spread out and charge plates - - - - - - -

  16. Electroscope – positive cond. Step 4 Scope is grounded – electrons from the ground are attracted to the positive scope Step 2 Electrons leave scope because they are attracted to the positive rod Step 5 Scope is once again neutral – balanced charge is restored Step 3 Scope is now positively charged Step 1 Positive rod touches neutral scope + - + - - - - + - +

  17. Electroscope – negative ind. Step 3 Rod is removed – electrons are attracted back to the top and “re-neutralize” the electroscope. Step 2 Scope polarizes as electrons at the top try to move away from the charged rod. Step 1 Negative rod brought near grounded scope - + - -

  18. Electroscope – positive induction Step 3 Rod is removed. Electrons are attracted back into the leaves by the protons, making the electroscope neutral again. Step 2 Electrons from the bottom of the electroscope are attracted to the positive rod – get pulled up. The leaves get a positive charge on them. Step 1 Positive rod is brought near neutral electroscope + - + - +

  19. Electroscope – ind. with ground Step 3 Ground is removed while the rod is still nearby, keeping electrons from re-entering the scope Step 5 The rod is taken away and the positive charge remains on the scope Step 4 Scope now has a charge that is opposite to the charge on the rod Step 2 Excess electrons from the rod force electrons from the scope into the ground. Step 1 Negative rod brought near grounded scope - + - - + - +

  20. Electroscope – ind. with ground Step 3 Ground is removed, while the rod is still nearby, pulling on electrons and keeping them from escaping Step 4 Scope is now negatively charged – the opposite charge as that of the rod Step 5 Rod is taken away and the negative charge remains on the scope Step 1 Positive rod is brought near grounded scope Step 2 Electrons from the ground are attracted to the positive rod + - - -

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