Internal resistance of batteries in a parallel circuit. |
In general, for resistors in a parallel circuit apply the formula... 1 / Ri = 1 / R1i + 1 / R2i + ... + 1 / Rni Your circuit consists of two 9-volt battery with an internal resistance of 1.2 Ω... 1 / Ri = 1 / R1i + 1 / R2i |
Circuit of two real batteries connected in parallel with a load resistance. |
You can rewrite the formula to get...
Ri = ( R1i * R2i ) / ( R1i + R2i ) = ( 1.2 Ω * 1.2 Ω ) / ( 1.2 Ω + 1.2 Ω ) = 0.6 Ω The internal resistance has become significantly smaller. This results in new values for the current and voltage in the load circuit, as you can see in the circuit shown. |
In any circuit that is powered by a battery, the internal resistance should be negligible compared to the resistance of the circuit. A parallel circuit is one possibility to reduce the internal resistance.
But there are also other advantages...
