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Real sources and lost volts

Real sources and lost volts

Circuit model of a real cell with e.m.f. E, internal resistance r, load R, current I, lost volts Ir, and a V-against-I graph showing intercept E and gradient -r A source of e.m.f. transfers energy to charge. Its e.m.f. EEE is the energy supplied per unit charge, so it is measured in volts, V. Despite the name, e.m.f. is not a force.

Internal resistance Lesson

  1. A Level
  2. /Physics
  3. /Internal resistance

Step-by-step lessons on OCR A A Level Physics Internal resistance. Each one builds up to exam-style questions. Physics is one of the most mathematically demanding A Levels -- at least 40% of the marks across the three papers require maths skills at Level 2 (GCSE) standard or above, so build calculation and graph-handling fluency alongside the conceptual content from the start.

Lessons