Find the work done, in joules, when an electric charge of 10 C moves across a potential difference of 2 V.

Introduction / Context:
In basic electricity, electric potential difference (voltage) is related to the work done in moving a charge between two points in an electric field. This question checks your ability to apply the simple formula that connects work, charge and potential difference. It is an example of a direct substitution problem that frequently appears in school-level physics exams.

Given Data / Assumptions:
- Charge moved, Q = 10 coulombs (C).
- Potential difference, V = 2 volts (V).
- We are asked to find the work done, W, in joules (J).
- We assume there are no energy losses and the entire work is associated with the potential difference given.

Concept / Approach:
The relationship between work done in moving a charge and potential difference is given by the formula:
W = Q * V
where W is work in joules, Q is charge in coulombs and V is potential difference in volts. This formula expresses that one volt is one joule of work per coulomb of charge. To solve the problem, you simply multiply the given charge by the given potential difference.

Step-by-Step Solution:
Step 1: Write down the formula connecting work, charge and potential difference: W = Q * V. Step 2: Substitute the given values Q = 10 C and V = 2 V into the formula. Step 3: Calculate W = 10 * 2. Step 4: This gives W = 20 joules. Step 5: Match the result with the options and select 20 as the correct answer.

Verification / Alternative check:
Check the units: coulombs multiplied by volts gives joules, since 1 V = 1 J / C. So Q * V = 10 C * 2 J/C = 20 J. The units are consistent, confirming that the calculation is dimensionally correct. The simple arithmetic also matches the intuitive expectation that doubling the potential difference or the charge doubles the work done, which is reflected in the formula.

Why Other Options Are Wrong:
5: This would correspond to using an incorrect factor or dividing instead of multiplying charge and potential difference.
40: This result would arise if you mistakenly doubled the correct answer or used 4 V instead of 2 V in the calculation.
10: This value suggests that only one of the numbers, charge or voltage, was used without properly applying the formula W = Q * V.

Common Pitfalls:
Students sometimes mix up the formula and incorrectly use W = V / Q or W = Q / V. Another common error is confusion between energy and power. Power involves time and is given by P = W / t or P = V * I, while this question deals only with work. Paying attention to units and remembering that voltage is energy per unit charge helps you recall the correct relation W = Q * V.

Final Answer:
The work done is 20 joules.