Answer:
a) Electric potential at Point A=66342.14v
Point B= -10800v
b) 928800J
Explanation:
Diagonal of the square= 0.25×1.414=0.35m^2
CornerA=kq1/A= (9×10^9)×(-3.3×10^-6)/0.35
=29700/0.35=-84857.14V
Kq2/A= (9×10^9)(4.2×10^-6)/0.25=37800/0.25=151200V
Sum= (-84857.14+151200)V= 66342.86v
Point B
Kq1/0.25= (9×10^9)(-3.3×10^-6)/0.25= -118800v
Kq2/0.35= (9×10^9)(4.2×10^-6)/0.35= 108000v
Sum= -118800+ 108000= -10800V
b) PE = q3×(sum of v)=2.1×10^-6)× 66342.86
PE= 928800V