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:

Allowance Method

An accounting technique that estimates and anticipates uncollectible accounts receivable and bad debts by establishing an allowance for doubtful accounts.

Bad Debts Expense

An expense recognized on a company’s income statement, representing the amount of accounts receivable that is not expected to be collected due to customers' inability to fulfill financial obligations.

Uncollectibles

Accounts receivable that a company has determined are unlikely to be collected and writes off as a bad debt expense.

Allowance Method

An accounting technique that anticipates and adjusts for potential future bad debts or credit losses.