Two Parallel Circular Plates, Each with a Radius Of $7.0 \mathrm {~mm}$

question 73

Multiple Choice

Two parallel circular plates, each with a radius of $7.0 \mathrm {~mm}$ and carrying equal-magnitude surface charge densities of $\pm 3.0 \mu \mathrm { C } / \mathrm { m } ^ { 2 }$ are separated by a distance of $1.0 \mathrm {~mm}$ with only air between them. How much energy is stored in these plates? (?₀ = 8.85 × 10^-12 C²/N ? m²)

• A)78 nJ
• B)25 nJ
• C)7.9 nJ
• D)250 nJ

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Useful Life

is the estimated duration of time an asset is expected to remain productive for the entity, used in calculating depreciation and amortization.

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