Three equal point charges, each with charge 1.45 μC , are placed at the vertices of an equilateral triangle whose sides are of length 0.450 m . What is the electric potential energy U of the system? (Take as zero the potential energy of the three charges when they are infinitely far apart.)

0.126J

Explanation:

To calculate the potential energy of the system U:

Since the charges are the same, and the charges between them are the same.

q1 =q2 = q3 are the charges, and r1=r2=r3 is the distance between their centres.

q = 1.45 μC

r = 0.450 m

1/4πE°(3q^2/r) 1

1/4πE° = 9 × 10^9 N⋅m^2⋅C−2,

Substitute the values into equation 1

= 9 × 10^9 N⋅m^2⋅C−2 × {3* (1.45×10^-6)^2/0.450m}

= 9 × 10^9 N⋅m^2⋅C−2×{3*2.1025^-12/0.450m}

= 9 × 10^9 N⋅m^2⋅C^−2×{6.3075^-12}/0.450m

= 9 × 10^9 N⋅m^2⋅C^−2 × 1.401^-11

= 0.12615J

= 0.126J

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