Two charges +6μC and −4μC are placed 15cm apart as shown. At what distances from A to its right, the electrostatic potential is zero?
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Correct option is
Let the potential be zero at point P at a distance x from the
charge +6×10−6C at A as shown in above figure.
Potential at P V=4πε01[x6×10−6−15−x(−4×10−6)] 0=4πε01[x6×10−6−15−x4×10−6] 0=x6×10−6−15−x4×10−6 x6×10−6=15−x4×10−6 ⇒6(15−x)=4x ⇒90−6x=4x ⇒10x=90 ⇒x=1090=9cm The
other possibility is that point of zero potential P may lie on
AB produced at a distance x from the charge +6×10−6C at A as shown in the figure. Potential at P V=4πε01[x6×10−6+(15−x)(−4×10−6)] 0=4πε01[x6×10−6−(x−15)4×10−6] 0=x6×10−6−(x−15)4×10−6 ⇒x6×10−6=x−154×10−6 ⇒x6=x−154 ⇒6x−90=4x ⇒2x=90 ⇒x=290=45cm