Potential Differences in a Circuit?

📌 CONCEPT: The potential difference across a circuit element, such as the power bank's terminals, is determined by the net potential difference developed across it when current flows through it.

📐 RULE / FORMULA: The potential difference (V) across a resistor in a circuit is given by Ohm's Law: V = IR, where I is the current flowing through the resistor and R is its resistance. However, in a real-world scenario like the power bank, the net potential difference is the sum of the potential differences across the internal and external resistances.

💡 WORKED EXAMPLE: Given a power bank with an internal resistance (R1) of 0.5 Ω, an external resistance (R2) of 10 Ω, and an internal resistance of the battery (r) approximately equal to the internal resistance of the power bank, the total resistance (R) of the circuit is R = R1 + R2. The total current (I) flowing through the circuit is given by I = 50000 mAh / 3600 s (since 1 Ah = 3600 C). The maximum potential difference (V) across the power bank's terminals is V = (I * (R1 + R2)) + (I * r).

⚠️ COMMON MISTAKE: Students often neglect the internal resistance of the battery and consider only the external resistance when determining the maximum potential difference across the power bank's terminals.