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(a) consider an arbitrary electrostic fieldconfiguration a small testcharge is placed at a null pointof the configuration show that the equailibrium of the test charge is necessarly unstable (b) verifythis resultfor the simple configuration of two charges of the same mangnitudeand sign placeda certain distance apart |
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Answer» SOLUTION :(a) prove it by contradiction SUPPOSE the equlibriumis stable then the test chargedisplaed slighly in any direction will experiencea retoring force towards the null pointthat is there is a net inward flux of electric field througha closed surface arougn the null point butgauss law the flux of electric fieldthrougha surface not enclosing any chargemust be zero hence the equilibrium cannotbe stable (b) the mid pointof theline joining the two chargesis a null pointdisplacea testchargfrom the null pointslighly ALONGTHE the linerememebr stabilityof equibrium needs restoring forcein alldirection |
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