Problen 7 In the picture below, the 3 charges Q1, Q2 and Qz are located at posit

Question

Problen 7 In the picture below, the 3 charges Q1, Q2 and Qz are located at positions (-a.0), (a,0) and (0,-d) respectively. (The origin is the point halfway between Q, and Q2.) Q1, al a_2, Consider the special case where Q1, Q; greater than zero and Q =-Q1. Which of the following statements are true? (Choose all correct answers e.g. ABD. CDFG). A) If Q; is released from rest, it will initially accelerate to the right. B) The force on Q; due to the other two charges is zero. C) The electric potential at the origin equals Q3/4Teod D) The electric field at the origin points in the positive y direction, away from Q3 E) The work required to move Q; from its present position to the origin is zero. F) The electric potential at any point along the y-axis is positive. G) The external work done to bring these charges to this configuration (from infinity) was positive. Submit Answer Tries 0/6 In the previous problem, let Q1=1.30 aC, Q2=-2.50 uc, and Q3=3.50 uC. (Note that Qi and Q2 are different now.) The distances are a=1.20cm and d=2.80 cm. Calculate the total electrostatic potential energy of the charge configuration, Submit Answer Tries 0/6

Explanation / Answer

Given

three charges Q1,Q2,Q3 .

Q1,Q2 are greater than zero and Q2 = -Q1

Q1,Q2 are along the X axis separated by a distance of a m on either side of origin

and Q3 is located on -y axis at d distance

A) as Q1 is -ve charge and Q2,Q3 are +ve charges , by symmetry the charge Q3 moves to left

B) no the net force is not equal to zero

C) yes the electric potential at origin is kQ3/d

because Q1,Q2 are of opposite charges and are at equidistance from origin stheir potential contrubutioin at origin is zero so remaining potential is only due to charg Q3  

D) due to Q1,Q2 the field direction is to the -y direction and due to Q3 , the field direction is along +y direction,

if a = d , then this is not true . it depends on the magnitude of the charges and the distance from the origin of each charge

E) yes, the potential is zero at origin due ot Q1,Q2 so the work required is zero long the y axis

F) electric potential i s V = kQ/r

V = k*Q3/d

so it is positive

G) no , there would be some electric field , so the work done is not zero

-------------

Q1 = 1.30*10^-6 C, Q2 = -2.5*10^-6 C , Q3 = 3.50*10^-6 C

and a = 1.2 cm , d = 2.8 cm

we know that the potential energy of the two charge system is U - kQ1*q2/r

here U12 = k*Q1*Q2/(2a) , U13 = kQ1*Q3/(sqrt(a^2+d^2) and  

U23 = k(Q2*Q3)/(sqrt(a^2+d^2)

U = k((Q1*Q2)/(2a) + (Q1*Q3)/(sqrt(a^2+d^2) + (Q2*Q3)/(sqrt(a^2+d^2))

substituting the values  

U = 9*10^9((1.30*10^-6*-2.5*10^-6)/(2*0.012)+(1.30*10^-6*3.5*10^-6)/(sqrt(0.012^2+0.028^2))+(-2.5*10^-6*3.5*10^-6)/(sqrt(0.012^2+0.028^2))) J

U = -2.459595790 J

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.