Energy stored by charges at a given potential difference How much energy (in joules) is stored when 6.24 × 10^18 electrons are placed at a potential of 4 V (use E = Q * V and 6.24 × 10^18 electrons ≈ 1 coulomb)?

Introduction / Context:
This problem checks your understanding of the relationship between electric charge, potential (voltage), and energy in basic circuit theory. When charges are moved through a potential difference, electrical potential energy is stored according to E = Q * V. Knowing the common equivalence 6.24 × 10^18 electrons ≈ 1 coulomb is a standard electronics shortcut.

Given Data / Assumptions:

• Number of electrons n = 6.24 × 10^18.
• Elementary charge e ≈ 1.602 × 10^-19 C per electron.
• Voltage V = 4 V.
• Neglect any losses; treat all charge at the stated potential.

Concept / Approach:
First convert the count of electrons into total charge using Q = n * e. Then compute energy with E = Q * V. In many introductory problems, 6.24 × 10^18 electrons is used because it is essentially one coulomb of charge (to three significant figures), which makes the arithmetic straightforward and reinforces unit intuition.

Step-by-Step Solution:
Compute total charge: Q = n * e ≈ (6.24 × 10^18) * (1.602 × 10^-19) ≈ 1.00 C.Apply energy formula: E = Q * V.Substitute values: E ≈ 1.00 C * 4 V = 4 J.Therefore, the stored energy is 4 joules.

Verification / Alternative check:
Dimensional analysis: coulomb times volt equals joule, which confirms unit consistency. The electron-count-to-coulomb equivalence is also consistent with 1 C ≈ 6.24 × 10^18 electrons.

Why Other Options Are Wrong:
1.56 × 10^18 electrons: this is a charge count, not energy.1.56 coulombs: incorrect charge; the given electron count equals about 1 C, not 1.56 C.2.496 × 10^19 electrons: incorrect and still not an energy unit.

Common Pitfalls:
Confusing charge, voltage, and energy units; forgetting to convert electron count to coulombs; or attempting to use capacitor energy formulas without a capacitance value. Here, E = Q * V is sufficient.

Final Answer:
4 joules