voltage dividers

[libby6295]

How could I use a voltage divider to answer this question?

In the manufacturing of car batteries, should the batteries have a very low internal resistance or a very high internal resistance?

[altenbach]

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@libby6295 wrote:

In the manufacturing of car batteries, should the batteries have a very low internal resistance or a very high internal resistance?

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Can you explain what this generic question has to do with voltage dividers?

[libby6295]

A low internal resistance is preferable but how could you illustrate this using a voltage divider?

[tipa]

Привет! В графическом виде, с использованием параметрического анализа, Вас устроит?

[tipa]

[GGoodwin]

Hi libby6295,

Let:

Vbatt = the battery's terminal voltage when there is no load connected (the battery's open-circuit voltage)
Rbint = the battery's internal resistance
Rload = the load (resistance)
Vload = the battery's terminal voltage when the load is connected

When the load is connected the circuit is shown in the image below

By voltage divider formula:

             Rload
Vload = ─────────────── Vbatt
         Rload + Rbint

From the above formula we can see that for a particular value of Rload,

• if Rbint is small, the denominator is small so the battery's terminal voltage (Vload) tends to be high

• if Rbint is large, the denominator is large so the battery's terminal voltage (Vload) tends to drop

Hence for a voltage source such as battery, it is desirable to have a small internal resistance.

Best regards,

G. Goodwin