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Electric Charges And Fields

Question

A system has two charges q_A = 2.5 x 10^–7 C and q_B = –2.5 x 10^–7 C located at points A: (0, 0, –15 cm) and B: (0, 0, + 15 cm), respectively. What are the total charge and electric dipole moment of the system?

Solution

Given,
Charge on A, q_{A = $2.5 \times 10^{- 7} C$}Charge on B, q_B=

- 2.5 \times 10^{- 7}

C

Therefore, total charge is q

q = q_{A} + q_{B} = 2.5 \times 10^{- 7} - 2.5 \times 10^{- 7} = 0

distance between two charges, a = AB = 15 – (– 15) = 30 cm = 0.3 m
Electric dipole moment

p = q . a

= 2.5 \times 10^{- 7} (0.3 m) = 7.5 \times 10^{- 8} Cm (along - Z - axis) .

[because the direction of dipole is always from (-)ve to (+)ve.]