Describe an investigation which suggests that battery cells have internal resistance?
Answer:
Connect a 2 V battery to a low resistance, say 0.5 ohms. you expect a current of 4 A. Actually, when you measure it will be less than 4A. Suppose it is 2A. This means that the total resistance in circuit is 1 Ohm. Where did this additional 0.5 ohm come? It is the internal resistance of battery.
with no load connected to the battery, measure the voltage. call it v1
put a 1 ohm resistor across the battery and again measure the voltage ,,, call this v2
notice that v1 > v2
a "ballpark" estimate of the internal resistance of the battery, Ri:
Ri = (v1 - v2) / v1
( units of Ri are in ohms )
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