Practice portal › Electric Charge and Properties › Electric Field of Point Charges
Asked in GUJCET 2020 · Field of discrete charges
Given: q = 10⁻⁸ C (one positive, one negative), separation 0.1 m, so each charge is r = 0.05 m from the centre.
Idea: at the midpoint the field of +q points away from +q and the field of -q points towards -q, the same direction, so the magnitudes add.
Field of each: E₁ = (kq)/(r²) = ((9×10⁹)(10⁻⁸))/((0.05)²) = (90)/(2.5×10⁻³) = 3.6×10⁴ N C⁻¹
Total: E = 2E₁ = 7.2×10⁴ N C⁻¹, directed towards the negative charge.
So the field at the centre is 7.2×10⁴ N C⁻¹.
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