Combination of Cells
To increase the amount of current or potential difference required in a circuit we can add cells to the circuit. This can be achieved in two different ways:
 Parallel Combination:
In parallel combination, the cells are connected in such a way that the potential difference of the circuit is same as the cells used in the circuit but the time of current flowing increases. The positive terminal of all the cells are connected to a single point and then connected to the positive terminal of the circuit and similarly, the negative terminal of all the cells are also connected to another single point and then connected to the negative terminal of the circuit. The cells that are used must have same potential difference. Cells with the different potential difference cannot be used in parallel combination. In this type of combination the potential difference between any two points in a circuit is the same and is equal to the individual potential difference of the cells used i.e. V = V_{1} = V_{2 }= V_{3}. In this combination the current provided by the cells is small and continuous for longer period of time. If we increase the number of cells the current cannot be increased but time of supply is increased.
 Series combination:
In series combination, the positive terminal of the first cell is connected to the negative terminal of the second cell and positive terminal of the second cell is connected to the negative terminal of the third cell and so on. In this combination of a cell, the overall potential difference is the sum of all the individual potential differences of the cells used in the circuit.
i.e. V = V_{1} + V_{2}+ V_{3}+ ...+ V_{n}.  . The current in the resistance in the series combination of cells is number of times the current due to individual cell. So, the current is larger but for shorter period of time. When we increase the number of cells in the series combination potential difference and current both increases.
 To increase the amount of current or potential difference required in a circuit we can add cells to the circuit. This can be achieved in two different ways:
 The cells which are connected in such a way that the potential difference of the circuit is same as the cells used in the circuit but the time of current flowing increases is known as parallel combination. (V = V_{1} = V_{2} = V_{3}….)
 In series combination positive terminal of first cell is connected to the negative terminal of the second cell and positive terminal of second cell is connected to the negative terminal of third cell and so on. (V = V_{1} + V_{2} + V_{3} + …. )
The characteristics of parallel combination of cells are as follows: 
 The potential difference between any two common points is always constant.
Total potential difference, V = V_{1} = V_{2} = V_{3}  The current is provided to the external resistance (R) for a longer time. (If the total internal resistance of cells is neglected)
 The magnitude of the electric current cannot be increased by a parallel combination of the cells.
Any three characteristics of series combination of cells are as follows: 
 The total potential difference (voltage) is equal to the sum of the individual potential difference of the cells.
Total voltage (V) = V_{1} + V_{2} + V_{3}
 The current in the external resistance (R) is the number of times the current due to a single cell. Hence, this type of combination is used when current is required for a short time.
 The magnitude of the electric current can be increased by a series connection of cells.
Parallel combination of cells  Series combination of cells 
In this combination, the positive terminals of the cells are connected to the one point and negative terminals to another point.  In this combination, the negative terminal of one cell is connected to the positive terminal of another cell and so on. 
Current flowing through the circuit remains constant even when more cells are added. V = V1 = V2 = V3 
Adding more cells can increase current flowing through the circuit. V = V1 + V2 + V3 
It is used when current is required for long time.  It is used when large amount of current is required. 
Total voltage (V) = V1 + V2 + V3 + ……….Vn
Given,
;Potential difference (v) = 6V value of one resistance R_{1} = 3Ω
Value of second resistance R_{2} = 6Ω
(a) Total resistance R= R_{1} +R_{2}
=3 + 6
= 9Ω
(b) Now from Ohm's law, we get V = IR
or, I= \(\frac{V}{R}\)
=\(\frac{6}{9}\)
= 0.67A
Hence, total resistance = 9Ω and current flowing through the circuit is 0.67 A

In which combination the cells are connected in such a way that the potential difference of the circuit is same as the cells used in the circuit but the time of current flowing increases?
Parellel combination
none of above
Mixed combination
Series combination

Potential difference is added in ______.
series combination
parallel combination
none of above
mixed combination

Equivalent resistance is addded in ______.
;i:3;s:13:
;i:2;s:17:
;i:1;s:20:

In a parallel circuit there are 3 resistors with voltages of 2 V, 2 V and 2 V, what is the voltage across the battery in the circuit?
2V
4V
1/ 6V
8 V

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