Cells in parallel

[TheLivingMartyr]

I have just had a go at an a-level physics past paper, (a bit ahead of time I might add), and one of the questions i had no clue on was a circuit diagram with 4 cells, each with emf 1.5V (negligible internal resistance), and 3 resistors, giving a total circuit resistance of 6Ω. The resistors are not a worry (as I can work out the total resistance, although I know the total resistance will be needed), but the cells are confusing me. The circuit was arranged thus: Two cells in parallel with each other, two cells in series, and those two elements in series with each other.

 

I do not know how to calculate the total emf of the circuit from this information, as I don't know the relationship between cells in parallel, and how you would add the emfs. The answer was: Total emf = 4.5V

 

Could someone please tell me the steps one must go through to find out total voltage and emf when cells are in parallel.

[TonyMcC]

The two cells in parallel only give you the same voltage as one cell on its own. (1.5V) You can say that the total voltage would therefore be the same as three 1.5V cells connected in series. i.e. 4.5V. This assumes the cells are all connected "the same way round".