Physics 3B, Exam 1 Multiple Choice) +24 3a +q -3a O are located on the x-axis of

Question

Physics 3B, Exam 1 Multiple Choice) +24 3a +q -3a O are located on the x-axis of a coordinate system as shown above. The charge +g is located at -3a. Where 1. Two charges charge +24 is located at x- +3a and the on the r-axis should an additional charge +4g be located to produce an electric field equal to zero at the origin 0? (B) -2a (D) x= +2a 0,3 m 2. A uniform electric field E of magnitude 6,000 V/m exists in a region of space as shown above, what is the electric potential difference, Vr-V, between points X and Y? (A) -12,000 v o V (c) 1,800 V (D) 2,400 v (E) 3,000 V

Explanation / Answer

since both are positive charges, EF will be zero in between the charges

let this location x units from +2q charge where an addition 4 Q charge is placed

so

ENt at Origin = 0

E1 + E2 + E3 = 0

k*2q/9a^2 - k q/9a^2 + k * 4q/x^2 = 0

2/(9a^2) - 1/(9a^2) + 4/x^2 = 0

4/x^2 = 1/9a^2

a^2/x^2 = 1/36

x/a = sqrt 36

x = 6*a option E-
--------------------

EF = dV/dx

dV = E * dx

dV = 6000* sqrt(0.3^2 + 0.4^2)

dV = 3000V option E

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