Practical circuits flashcards

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What is the fundamental difference between electromotive force (e.m.f.) and terminal potential difference (p.d.)?

E.m.f. is the total energy supplied per unit charge by the source (including internal losses), while terminal p.d. is the voltage available across the external load after accounting for internal resistance.

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Which conservation principles are embodied by Kirchhoff's First and Second Laws, respectively?

Kirchhoff's First Law is based on the conservation of charge, and Kirchhoff's Second Law is based on the conservation of energy.

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How does internal resistance affect the voltage delivered to an external load?

Internal resistance causes a 'lost voltage' (v = Ir) internally, reducing the terminal potential difference (V = ε - v) available to the external load.

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What is the main application of a potential divider circuit?

To split a larger supply voltage into a smaller, desired output voltage, or to create a variable output voltage using a potentiometer or sensor.

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When calculating total resistance, what is the key difference in approach for series versus parallel circuits?

For series circuits, resistances add directly (R_total = ΣR_i); for parallel circuits, the reciprocals of resistances add (1/R_total = Σ1/R_i).

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What are 'lost volts' in a practical circuit?

'Lost volts' refer to the potential difference dropped across the internal resistance of a power source when current flows, causing energy dissipation within the source itself.

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State Kirchhoff's First Law.

The sum of currents entering any junction in a circuit must equal the sum of currents leaving that junction, reflecting conservation of charge.

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Under what condition is maximum power transferred from a source to an external load?

Maximum power is transferred when the external load resistance (R) is equal to the internal resistance (r) of the power source.