Question

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1. Two charges of 𝑞1=+ 12.0 𝑛𝐶 and 𝑞2=− 12.0 𝑛𝐶 are 0.100 m apart (such pairs of point charges with equal magnitude and opposite sign are called electric dipoles.). Calculate the electric field caused by 𝑞1.

2. Two charges of 𝑞1=+ 3.0 𝑛𝐶 and 𝑞2=− 7.0 𝑛𝐶 are separated by a distance of 50 cm. What is the electric field strength at a point that is 20cm from 𝑞1 and 30cm from 𝑞2? The point lies between 𝑞1 and 𝑞2.

Answer 1

1.

$E=\frac{kq_1}{r^2}=10.8~\frac{kN}C.$

2.

$E=k(\frac{q_1}{r_1^2}-\frac{q_2}{r_2^2})=1375~\frac NC.$