A parallel plate capacitor is made of two circular plates separated by a distance of 5 mm and with a dielectric of dielectric constant 2.2 between them. When the electric field in the dielectric is 3×10⁴ V m⁻¹, the charge density of the positive plate will be close to

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(2) 6×10⁻⁷ C m⁻². Inside a dielectric the free charge density on the plate is fixed by E=σ/(Kε₀), so σ=Kε₀E. Kε₀=2.2×8.85×10⁻¹²=1.947×10⁻¹¹. σ=1.947×10⁻¹¹×3×10⁴=5.84×10⁻⁷ C m⁻². This is close to 6×10⁻⁷ C m⁻². (The plate separation of 5 mm is not needed.)

A parallel plate capacitor is made of two circular plates separated by a distance of 5 mm and with a dielectric of dielectric constant 2.2 between them. When the electric field in the dielectric is 3×10⁴ V m⁻¹, the charge density of the positive plate will be close to

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