In a series combination of cells , the effective internal resistance will increase or decrease?
Answers
Electromotive Force and Internal Resistance:
The electromotive force (e) or e.m.f. is the energy provided by a cell or battery per coulomb of charge passing through it, it is measured in volts (V). It is equal to the potential difference across the terminals of the cell when no current is flowing.
e = E/Q
e = electromotive force in volts, V
E = energy in joules, J
Q = charge in coulombs, C
Batteries and cells have an internal resistance (r) which is measures in ohm’s (W). When electricity flows round a circuit the internal resistance of the cell itself resists the flow of current and so thermal (heat) energy is wasted in the cell itself.
e = electromotive force in volts, V
I = current in amperes, A
R = resistance of the load in the circuit in ohms, W
r = internal resistance of the cell in ohms, W
We can rearrange the above equation;
e = IR + Ir
and then to
e= V + Ir (because V=IR)
In this equation (V) appears which is the terminal potential difference, measured in volts (V). This is the potential difference across the terminals of the cell when current is flowing in the circuit, it is always less than the e.m.f. of the cell.
Now, if all cells able to produce enough current, and R is superconductor(resistance is zero) then sometimes there will be maximum current flowing through the circuit, when all cells are connected in parallel connection. (Generally when r > 1 ohms, and e = 1V, 2V, 3V....... ... )
In a series combination of cells, the effective internal resistance increases.
In a series combination of cells, all the cells are joined end to end. Hence all the internal resistances are basically in a series arrangement. Also, all the batteries are also in a series arrangement. Therefore the net voltage is the addition of the voltages of the cells. While the net internal resistance is the addition of all the internal resistances. Therefore the net internal resistance increases.
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