Question

Four charges of 6mC, 2mC, – 12mC and 4mC are placed at the corners of a square of side 1m. The square is in x-y plane and its center at its origin. Electric potential due to these charges is zero everywhere on the line –

• A. x = y, z = 0
• B. x = 0 = z
• C. x = 0 = y
• D. None

Answer 1

Answer: (C)

x = 0 = y

Answer 2

$\sum \frac { Q } { r }$ = 0 at x = 0 = y

= $\frac { 4 } { \mathrm { r } }$ + $\frac { 6 } { r }$ – $\frac { 12 } { \mathrm { r } }$ = 0