Question

Two point charges +4nc and +1nc are separated by 30cm in air find the position between them at which the resultant electric field is zero from the bigger charge ​

Answer 1

Two point charges +4nC( q1) and +1nC(q2) are separated by 30cm in air

The point at which the resultant electric field is 0, say the point is at a distance of x cm from the bigger charge +4nC , so the distance from the other charge is (30 - x) cm

• The electric field created by a charge of q at a distance r is given by:

                                  E = kq/r²

so, the resultant electric field from the two charges is E = E1+ E2

                       E = kq1/x² - kq2/(30-x)² = 0

• or,          q1/q2 = x²/(30-x)²
• or,          √4 = x/(30-x)
• or,           60-2*x =x
• or,            x = 20

The distance from the bigger charge is 20 cm