Batteries connected in parallel and resistance

[Oerg]

Homework Statement

What i may ask may seem simple, but it is casuing me a lot of headaches. What is the effective potential difference across a resistor if it is connected to a parrallel connection of batteries. Let's quantify the variables. Battery one has an e.m.f. of 2 V while battery 2 has an e.m.f. of 6V. Resistor has a resistance of 7ohms.

Homework Equations

Kirchoff's spotential difference law

The Attempt at a Solution

Ok, according to kirchhoffs second law, for any closed loop, the algebraic sum of potential difference is 0. But for both closed loops, the potential difference across the resistor is different. So what really happens in this case? Will the potential difference across the resistor be 5V and the 2V battery does not release a current at all? Please help. Surely this is not the case.

 

[Astronuc]

The lower potential battery is something of a short circuit across the higher potential battery, so some energy (current) from the higher potential battery flows to the lower one. Both batteries would have some internal resistance (usually low).

 

[mjsd]

note the problem here is that you have connect two supposedly ideal voltage source in parallel 6V vs 2V, each will try to maintain a different voltage at the common terminal! that means normal ideal circuit analysis assumptions cannot be applied for your circuit is inconsistent (it is like saying terminal AB must be 6V and 2V simultaneously which cannot happen in a classical world). That is why you are getting a contradiction when applying your rules.

 

[Oerg]

Hmm so what really happends if we were to set up such a connection in reality? What assumptions of an ideal battery might be compromised?

 

[pooface]

I wouldn't advise you to try this. In first semester we learned to never connect batteries of different voltages in parallel. the result will be bad.

Batteries of equal potential must be carefully considered for this as they should be exactly the same. They will produce half the current each to the resistor.

 

[Manisha jadav]

The lower potential battery is something of a short circuit across the higher potential battery, so some energy (current) from the higher potential battery flows to the lower one. Both batteries would have some internal resistance (usually low).

if i connect 1.5 v battery of internal resistance 0.5 ohm in parallel with 1.2 v cell of 0.7 ohm internal resistance what will happen?
and if i connect whole ckt to the infinity load than what would be the power diliverd by the battery?

 

[ashishsinghal]

I wouldn't advise you to try this. In first semester we learned to never connect batteries of different voltages in parallel. the result will be bad.

What kind of result can we expect. Can it happen that the batteries will also be charged/discharged in such a manner that both of them have same potential.

 

[Manisha jadav]

i have one exercise about it and i don't know how to calculatwe pls tell me calculation

 

[gneill]

Draw the resulting circuit (be sure to include the battery internal resistances). Apply Kirchhoff's and Ohms laws to analyze it.

 

[ramesh29]

Define voltage & current batteries in parallel
V= increase I= same
In series what ?

 

[ramesh29]

Identical natures of battery
in series the emf varies at load as increase in voltage & current remain same
the polarity tune as +to - Or -to +

in parallel case it is consider to batt of same range in voltage & internal registance
in this case amp increase but voltage remains same