Measuring Internal Resistance - PRACTICAL - A Level Physics

In this video I go through an AQA Physics A Level Required Practical that uses an electrical circuit experiment to measure the internal resistance of a cell or battery. (This is AQA Required Practical 6.) This is also the OCR A Level Physics PAG 3.3 Practical.

Internal resistance is the electrical resistance within the cell or battery that is powering the circuit. Measuring internal resistance can be done by changing the external resistance of the circuit and recording the terminal p.d of the cell. When a graph is plotted the gradient is the negative value of 'r' while the y-intercept should be equal to the e.m.f. of the cell.

Thanks for watching,

Lewis

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[mubafaw]

Literally made my day and was able to use this to analyse to different sets of cells and the results were astonishing! Thank you!! 😀

[jackvanbenthuysen]

Wow thanks! I am taking an electricity and optics lab but because of covid it is all online and you are doing a better job at explaining this than my professor and TAs

[brightspark]

Hi, I was wondering what some of the key risks to consider are

[TehRossyy]

Thank you for this video however what is the point in the switch?

[matteo]

Why doesn’t putting the voltmeter across the terminals give us electromotive force? Isn’t it measuring the pd of the terminal and the internal resistance?

[yousefsayed]

I don't know but if we want to measure the internal resistance of voltameter we should put the voltameter in series with the circuit, I know it have too much resistance, so we can measure it?

[seanki]

Thanks for the video sir! I was just wondering- wouldn't you need a fixed resistor to be in the circuit as well in order to have a better control of the current- for safety reasons?

[mahinchowdhury]

It was an amazing explanation. Thank you 😄

[michalmasiak]

Nice, but... What is the point of taking a few measurements? I see two: a) ascertain that internal resistance is linear in the range of drawn currents (because you obtain a straight line with certain slope) (and this does not need to be the case), and b) accuracy of the measurements. But technically, you could get this "internal resistance" using just a single measurement and dividing U/I. So, my question is: do you really get the true EMF and internal resistance using this method?

[sajaniskumar]

Sir, Will the resistance of the voltmeter and ammeter affect the calculation??

[jordangatt]

This was so helpful. You made it interesting. Thanks! :)