What is the charge q? Give your answer in nC.?

Question

An electric dipole is formed from two charges,+/- q , spaced 1.40 cm apart. The dipole is at the origin, oriented along the y-axis. The electric field strength at the point (x,y) = (0cm,10cm) is 390 N/C.

a) What is the charge q? Give your answer in nC.

b) What is the electric field strength at the point (x,y) = (10cm,0cm)?

Answer 1

Et= E1 + E2

E1 = kQ/R1^2

E2 = kQ/R2^2

R1= 10 + 1.4 / 2

R2= 10 -1.4 / 2

Et = E1 + E2= kQ( 1/R1^2 - 1/R2^2 ) (negative sign since they are apposite )

Q= Et /[k (1/R1^2 - 1/R2^2 ))

b) Again

Et = E1 + E2

Et= (E1 - E2)=kQ(1/R1^2 - 1/R2^2 ))

R1=R2= sqrt( (1.4/2)^2 + 10^2)