physics 1. Consider a test charge of +3.75 nC placed on the x-axis at a point th

Question

physics 1. Consider a test charge of +3.75 nC placed on the x-axis at a point three-sixteenth the distance from to Q2 (QI and Q2 being two equal (in all respects) charges fixed on the x-axis If the electric force on this charge is 1.25x10 N and directed Qh find the magnitude of each charge. (Correct sketch is worth 2 10 points) d 8 0 2. Two point charges +57.8 HC and +20.0HC fixed on the x-axis are separated by a distance of 27.0 cm from each other. point along the x-axis is the electric field zero? sketch that demonstrates there is one and only one is worth 3 points out of 10) 20

Explanation / Answer

1)

let q = 3.75 nC

Q1 = Q2 = Q

distance from Q1 to q, r1 = (3/16)*80 = 15 cm = 0.15 m

distance from Q2 to q, r2 = (13/16)*80 = 65 cm = 0.65 m

now use, Fnet = k*q*Q1/r1^2 - k*q*Q2/r2^2

1.25*10^-5 = 9*10^9*3.75*10^-9*Q/0.15^2 - 9*10^9*3.75*10^-9*Q/0.65^2

1.25*10^-5 = 1420*Q

==> Q = 8.8*10^-9 C

= 8.8 nC <<<<<<<-------Answer

2) let x is the distance from Q1 where Enet = 0

k*Q1/x^2 = k*Q2/(d-x)^2

Q1/x^2 = Q2/(d-x)^2

(d-x)/x = sqrt(Q2/Q1)

(27 - x)/x = sqrt(20/57.8)

27 - x = 0.588*x

27 = 1.588*x

==> x = 27/1.588

= 17 cm <<<<<<<-------Answer

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