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Two point objects carry positive charges of magnitude 5e and 20e . Separation between the charges is 1 cm. Find the location of points on the line joining the two charges where the electric field intensity is zero. |
Answer» Solution :As the TWO charges are of same polarity thus, electric field will be zero at a point between the two charges . Let a point M be LOCATED between the two charges where electric field is zero. Given : `Q_1=5e=5xx1.6xx10^(-19)` C `Q_2=20e=20xx1.6xx10^(-19)`C At M, `E_1=E_2` `rArr 1/(4piepsilon_0)Q_1/x^2 =1/(4piepsilon_0)Q_2/(0.001-x)^2` `rArr Q_1/x^2=Q_2/(0.01-x)^2` `rArr (5xx1.6xx10^(-19))/x^2 =(20xx1.6xx10^(-19))/(0.01-x)^2` `(0.01-x)^2/x^2=20//5`=4 `(0.01-x)/x=pm2` `rArr x=+1/300m =+1/3 cm` and `x=-1/100` m =-1 cm x=-1 cm lies on the LEFT side of charge `Q_1`, but on the left side of `Q_1`, the electric fields due to `Q_1` and `Q_2` will be in the same direction, so the net electric field cannot be zero. The electric field is zero only at `x=+1/3` cm from charge `Q_1` between the two charges. |
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