# Lecture2 - Charge mobility in conductors, an electroscope...

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Charge mobility in conductors, an electroscope • The top metal knob is connected to the metal bar and needle in the center, but insulated from the uter frame and the ground outer frame and the ground. • Like-sign repulsion causes the needle to deflect if charge can be transferred to the inner part of the electroscope.

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olarizing the electroscope Polarizing the electroscope Notice that the electroscope will indicate charge even if the rod is brought near, but not touching the top knob. A positive charge on the rod pulls negative charge to the knob, leaving the needles and support positively charged. hat happens to the needle when the rod is removed? What happens to the needle when the rod is removed? A. It does not move and remains deflected. B. It returns to its un-deflected position and stays there. C. It returns to its un-deflected position, and then deflects again.
duced charge on an electroscope Induced charge on an electroscope If we generate charge separation (or polarization) by bringing the positive rod close to the electroscope and then touch the needle section, the positive charge on e needle will be grounded out but the negative the needle will be grounded out, but the negative charge on the knob will be held in place by the charged rod. If we remove our hand from the needle and then pull the rod away from the knob, what will charge on the electroscope be? ositive A. Positive. B. Zero. C. Negative.

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uilding Up E- ields by Superposition Building Up E Fields by Superposition •The electric field produced by one charge is, | | | | 1 4 1 ) , ( 2 0 i i i i i i r r r r r r Q r r E r r r r r r r r r × × × = πε •The labeling is changed a little to help with what is to follow. Q i is the charge producing the field, r i is where the
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## This note was uploaded on 05/11/2010 for the course ＰＨＹ 214 taught by Professor Timothybolton during the Spring '10 term at Kansas State University.

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Lecture2 - Charge mobility in conductors, an electroscope...

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