The electrostatic potential energy U between two point charges is given by the formula:
U=rkq1q2,
where:
- k=4πϵ01 is Coulomb’s constant,
- q1=7mC=7×10−3C,
- q2=−4mC=−4×10−3C,
- r is the distance between the charges.
We can calculate the distance r between the charges using the distance formula:
r=(7−(−7))2+(0−0)2+(0−0)2=(14)2=14m.
Now, using the value of Coulomb's constant k=4πϵ01:
k=4π×8.85×10−121=9×109N⋅m2/C2.
Substitute the values into the formula for potential energy:
U=149×109×(7×10−3)×(−4×10−3).U=149×109×(−28×10−6)=−18J.
Thus, the electrostatic potential energy is −18J.