four 9 volt batteries are connected in parallel. how much voltage is active across the circuit?

9 volts, if the polarity of each is the same. Otherwise you will get a lot of smoke.

Connect them in series and you get 36 volts, again, if you connect them correctly.

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even whether it incredibly is purely a low priced, Radio Shack 5000 ohms in line with volt multi-meter, you quite do want one so as which you will discover for your self what you get once you do some thing alongside with what you have asked approximately. Seeing the voltage exchange, or stay the comparable is quite an extremely stable help for studying. Your 4 batteries, as others have already suggested is going to be 9 volts. the present ability of those 4 batteries in spite of the incontrovertible fact it incredibly is now going to be approximately 360 Milli-amps, consistent with a ability of ninety milli-amps in line with battery.

I just did an experiment using two 9 volt battary's and a volt meter. the result is that when battary's are connected in parallel the voltage stays the same and therefore the amperage is cumulative. when the battary's are connected in series the voltage is cumulative and the amperage stays the same. The wattage is always cumulative.

My question is how people like Bob can believe that connecting battary's in one fashion will increase both the voltage and amperage over another fashion but never conclude that if such a thing were possible it would also make energy-less wattage amplification possible?

If you connect any number of similar voltage batteries in a PARALLEL circuit you keep the voltage
the same, in this case it would be 9 volts, However connecting those same four batteries in a circuit
configured in SERIES would result in a 36 volts outcome and greatly increase the AMPERAGE that
results...CAUTION....CAUTION....BE VERY CAREFUL...when connecting LARGE BATTERIES..
of the automotive, truck,or heavy equipment variety you can develop tremendous amperage (which is HEAT) and it can become dangerous to work with, loose connections can result in melted battery connections fused (welded) cable connections and serious burns from hot.. I MEAN HOT..metal
that can be propelled from a poor connection towards the hands or face of anyone close...

There are two scenario.

1. They are connected with the same polarity together. The terminal voltage will be 9V. Due to variation in electrical property of individual battery, there is minor discharge to weaker batteries and the voltage will decrease very slowly. Batteries should not be stored in such condition.

2. Some batteries are connected with opposite polarity. This will result in quick discharge and generate large amount of heat or even fire. The terminal voltage will drop to very low.

36 volts.

d. 36 volts.