At distance r from a point charge q, the electric potential is 708 V and the magnitude of the electric field is 133 N/C. Determine the value of q. The Coulomb constant is 8.98755 × 109 N · m 2 /C 2 . Answer in units of C

4.19×10⁻⁷ C

Explanation:

Firstly we find the value of r, using

V = Er Equation 1

Where V = electric potential, E = electric Field, r = distance.

make r the subject of the equation

r = V/E Equation 2

Given: V = 708 V, E = 133 N/C.

Substitute into equation 2

r = 708/133

r = 5.323 m.

Using,

V = kq/r Equation 3

Make q the subject of the equation

q = Vr/k Equation 4

Where q = charge, k = coulomb constant

Given: V = 708 V, r = 5.323 m, k = 8.98755×10⁹ Nm²/C²

Substitute into equation 4

q = 708(5.323)/8.98755×10⁹

q = 4.19×10⁻⁷ C.

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