You measured the emf of the model battery with a multimeter. Why should this give you...

You measured the emf of the model battery with a multimeter. Why should this give you an accurate measurement of emf , considering that the battery has an internal resistance?

Expert Solution

The model battery is a voltage source with a internal resistance in series. When the battery is delivering no current, there is no current through this internal resistance, and therefore the voltage drop by it is 0. The open circuit voltage of a battery is therefore the same as its internal voltage.

When we put a load on the battery, current flows, the internal resistance drops some voltage, and the external voltage is then less than the internal voltage.

When we are measuring voltage with a multimeter it works as voltmeter.Voltmeters have high impedance (infiity for ideal voltmeter). Since voltmeter is connected in parallel with the element whose voltage is going to be measured so they present very low load to the battery that can be ignore for practical purposes. Therefore the internal and external voltages of the battery are same for practical purposes when measured with a multimeter.

Thus this give us an accurate measurement of emf.

* emf is a specific term used to describe a voltage generated by a battery.

genius_generous answered 2 years ago

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