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Internal resistance

Internal resistance. Teachers This PowerPoint presentation guides you through internal resistance and the classic experiment and graph. You can move onto the next slide when the green arrow appears.

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Internal resistance

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  1. Internal resistance Teachers This PowerPoint presentation guides you through internal resistance and the classic experiment and graph. You can move onto the next slide when the green arrow appears. The slides can be printed out as OHTs. If the background is changed to white, they will print faster.If you do not have a colour printer they will print to black and white. Students. Use the presentation for support or as revision. Go to “Slide Show” on the toolbar - then pull down to “View Show” START

  2. Internal resistance Internal resistance Useful terms : Potential Difference p.d. - the voltage between two points E.m.f. - electromotive force

  3. V Internal resistance The voltmeter in this circuit measuresthe e.m.f. e.m.f. = 1.27 V

  4. V A Internal resistance The voltmeter in this circuit measuresthe TERMINAL POTENTIAL DIFFERENCE t.p.d. The t.p.d. is always less than the e.m.f. Terminal Potential Difference = 1.13 V

  5. r V A Internal resistance t.p.d. is always less than the EMF The ‘lost volts’ is due to INTERNAL RESISTANCE of the battery Terminal Potential Difference = 1.13 V Lost volts = e.m.f - t.p.d. = 1.27 - 1.13 e.m.f. = 1.27 V = 0.14 V

  6. r I = 0.06 A V A Internal resistance Lost Volts = 0.14 V Lost volts = current x internal resistance Lost Volts = I x r 0.14 = 0.06 x r r = 0.14 / 0.06 = 2.3 W

  7. Internal resistance r V A e.m.f. = V + lost volts Useful formulae : Lost volts = I r E = I ( R + r )

  8. r V switch A Internal resistance The experiment! R What to do : Close the switch Vary the resistance Measure the current and the p.d.

  9. r V A R Internal resistance The results!

  10. Internal resistance The graph!

  11. 1.27 V Gradient = 2.3 0.55 A Internal resistance

  12. e.m.f. Gradient = r Max current Internal resistance p.d. Current Remember this graph! Finish

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