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

question 50

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? $\left( \varepsilon _ { 0 } = 8.85 \times 10 ^ { - 12 } \mathrm { C } ^ { 2 } / \mathrm { N } \cdot \mathrm { m } ^ { 2 } \right)$

• A) \(250 \mathrm {~nJ}\)
• B) \(25 \mathrm {~nJ}\)
• C) \(78 \mathrm {~nJ}\)
• D) \(7.9 \mathrm {~nJ}\)

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Definitions:

Direct Materials

Materials that can be directly attributed to the production of specific goods or services and are an essential component of finished products.

Fixed Overhead

Indirect costs of production that remain relatively constant regardless of the level of output, such as rent, salaries, and insurance.

Variable Overhead

Costs that fluctuate with the level of production output, such as utilities or raw materials.

Direct Labor

The wages paid to employees who are directly involved in producing goods or providing services.