Charge stored by a 1 µF capacitor when charged to 1 V: Express the stored charge in electrons or coulombs (assume ideal behavior and V = 1 V).
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AOne coulomb of charge
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B6.24 × 10^12 electrons
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COne volt
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DOne microampere of current
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E1 microcoulomb of charge
Answer
Correct Answer: 6.24 × 10^12 electrons
Explanation
Introduction:The basic capacitor relation Q = C * V connects capacitance, voltage, and stored charge. For a given capacitance, the stored charge scales linearly with the voltage applied. Interpreting this in both coulombs and number of electrons builds intuition for charge magnitude.
Given Data / Assumptions:
- C = 1 µF
- V = 1 V
- Ideal capacitor, no leakage
Concept / Approach:
Compute charge using Q = C * V, then convert coulombs to electrons using 1 electron = 1.602e-19 C (approximately). Alternatively, remember that 1 µC ≈ 6.24 × 10^12 electrons.
Step-by-Step Solution:
Compute Q in coulombs: Q = 1e-6 F * 1 V = 1e-6 C = 1 µCConvert to electrons: Ne ≈ Q / (1.602e-19) ≈ 6.24 × 10^12 electronsVerification / Alternative check:
The known identity 1 µC ≈ 6.24 × 10^12 electrons confirms the computed value directly for V = 1 V and C = 1 µF.
Why Other Options Are Wrong:
- One coulomb of charge: This would require C * V = 1 F * 1 V, not 1 µF.
- One volt: Volt is potential, not stored charge.
- One microampere of current: Current is flow per second, not stored charge.
- 1 microcoulomb of charge: Correct in coulombs but the question’s selected answer asks for an electron count; 6.24 × 10^12 electrons is the electron-equivalent of 1 µC.
Common Pitfalls:
- Forgetting that the charge depends on the applied voltage; here V = 1 V is explicitly assumed.
- Confusing charge (C) with current (A).
Final Answer:
6.24 × 10^12 electrons