A cell of constant electromotive force (e.m.f.) and negligible internal resistance is separately connected into four different circuits. In which circuit does the power dissipated by the lamp stay the same as the variable resistor is adjusted?

Physics

IGCSE&ALevel

CAIE

Exam No：9702_s25_qp_14 Year：2025 Question No：33

Answer:

Knowledge points:

10.1.1 recall and use appropriate circuit symbols as set out in the ASE publication Signs, Symbols and Systematics (example circuit symbols are given in Section 5.5.)

10.1.2 draw and interpret circuit diagrams containing sources, switches, resistors, ammeters, voltmeters, and/or any other type of component referred to in the syllabus

10.1.3 define electromotive force (e.m.f.) in terms of the energy transferred by a source in driving unit charge round a complete circuit

10.1.4 distinguish between e.m.f. and potential difference (p.d.) in terms of energy considerations

10.1.5 understand the effects of the internal resistance of a source of e.m.f. on the terminal potential difference

A cell of constant electromotive force (e.m.f.) and negligible internal resistance is separately connected into four different circuits. In which circuit does the power dissipated by the lamp stay the same as the variable resistor is adjusted?

Answer:

Knowledge points:

Solution:

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