Field and force with three charges At a particular moment, three small charged b

Question

Field and force with three charges

At a particular moment, three small charged balls, one negative and two positive,are located as shown in the figure. Q1 = 1 nC, Q2 = 5 nC, and Q3 = -3 nC.

Remember that you must first convert all quantities to S.I. units. 1 nC = 1 nanocoulomb = 1e-9 C.

N

Q#2:

An Fe3+ ion is located 400 nm (400 109 m, about 4000 atomic diameters) from a Cl ion, as shown in the figure below (ions not shown to scale).

(a) Determine the magnitude and direction of the electric field

at location A,

r = 144 nm

to the left of the Cl ion.

(b) Determine the magnitude and direction of the electric field

at location B,

r = 144 nm

to the right of the Cl ion.

(c) If an electron is placed at location A, what are the magnitude and direction of the force on the electron?

Explanation / Answer

Q#2)Given,

r = 400 nm ; Q1 = +3e ; q2 = -e

a)we know that,

E = kq/r^2

for the given system at A

E = E1 + E2

E = k (q1/r1^2 + q2/r2^2)

E = 9 x 10^9 x 1.6 x 10^-19 [3/(400-144) x 10^-6)^2 + 1/(144 x 10^-9)^2] = 1.35 x 10^5 N/C

Hence, E = 1.35 x 10^5 N/C

Directed towards right

b)E = 9 x 10^9 x 1.6 x 10^-19 [3/(400+144) x 10^-6)^2 + 1/(144 x 10^-9)^2] = 8.4 x 10^4 N/C

Hence, E = 8.4 x 10^4 N/C

Directed towards Left.

c)We know that,

F = q E

F = 1.6 x 10^-19 (1.35 x 10^5) = 2.16 x 10^-14 N

Hence, F = 2.16 x 10^-14 N

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