A charge of #-2 C# is at the origin. How much energy would be applied to or released from a # 4 C# charge if it is moved from # (-7 ,1 ) # to #(4 ,-2 ) #?

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Answer 1 · 2018-01-24T14:22:41

The energy applied is #=5.92*10^9J#

The potential energy is

#U=k(q_1q_2)/r#

The charge #q_1=-2C#

The charge #q_2=4C#

The Coulomb's constant is #k=9*10^9Nm^2C^-2#

The distance

#r_1=sqrt((-7)^2+(1)^2)=sqrt(50)m#

The distance

#r_2=sqrt((4)^2+(-2)^2)=sqrt(20)#

Therefore,

#U_1=k(q_1q_2)/r_1#

#U_2=k(q_1q_2)/r_2#

#DeltaU=U_2-U_1=k(q_1q_2)/r_2-k(q_1q_2)/r_1#

#=k(q_1q_2)(1/r_1-1/r_2)#

#=9*10^9*((-2)*(4))(1/sqrt50-1/sqrt(20))#

#=5.92*10^9J#