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Examples: Internal Resistance

<^< Internal Resistance | Course Index | Fuses >^>(:nl:)

>>frame round<< 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. >><<

>>id=example1 class=question margin=10px frame round<< Now V'_OUT_' = V - (I × R'_S_')

In this case, V'_OUT_' = 0.75 V, V = 1.5 V and I = 1 A.

Thus:

0.75 = 1.5 - (1 × R'_S_')

Hence:

0.75 - 1.5 = - (1 × R'_S_')

From which RS = 0.75 &#937; >><<

>>frame round<< Example 2:

A battery has a no-load voltage of 12 V and an internal resistance of 0.2 &#937;.

What voltage will the battery supply when it is delivering a current of 20 A? >><<

>>id=example2 class=question margin=10px frame round<< Now V'_OUT_' = V - (I × R'_S_')

In this case, V = 12 V and I = 20 A.

Thus:

V'_OUT_' = 12 - (20 × 0.2)

V'_OUT_' = 12 - 4

From which V'_OUT_' = 8 V >><<(:nl:)(:table style="clear:both":)