Two charges 5μC and −20μC are placed 30 cm apart. Find the strength of electric field at the mid point between them.
Let "O" be the midpoint between the charges Q1andQ2.
The strength of electric field at the point 'O' due to Q1 is.
E1=14πϵ0Q1d21
=9×109×5×10−6(0.15)2
=2×106N
The strength of electric field at the point 'O' due to Q1 is,
E2=14πϵ0Q2d22=9×109×20×10−6(0.15)2
=8×106N
Total strength of electric field at the point 'O' s E=E1+E2
=2×106+8×106=[2+8]106=107N