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Examples: Internal Resistance<^< Internal Resistance | Course Index | Fuses >^> Example 1:
When no load is connected to a battery its output voltage is 1.5 V. However, when the battery is delivering a current of 1 A, its output voltage falls to 0.75 V. Determine the internal resistance of the battery.
Now VOUT = V - (I × RS) In this case, VOUT = 0.75 V, V = 1.5 V and I = 1 A. Thus: 0.75 = 1.5 - (1 × RS) Hence: 0.75 - 1.5 = - (1 × RS) From which RS = 0.75 Ω Example 2:
A battery has a no-load voltage of 12 V and an internal resistance of 0.2 Ω. What voltage will the battery supply when it is delivering a current of 20 A?
Now VOUT = V - (I × RS) In this case, V = 12 V and I = 20 A. Thus: VOUT = 12 - (20 × 0.2) VOUT = 12 - 4 From which VOUT = 8 V <^< Internal Resistance | Course index | Fuses >^> |