Four cells each of emf 1.5V and the internal resistance 0.5 Ω are connected in series but one cellis wrongly co

It seems like your question got cut off. However, based on what you've provided, I can start explaining the concept.

When cells are connected in series, their emf (electromotive force) values add up. So, if you have four cells each with an emf of 1.5V, the total emf for the circuit would be 4 * 1.5V = 6V.

The internal resistance of the cells also adds up when the cells are connected in series. So, if each cell has an internal resistance of 0.5 Ω, the total internal resistance would be 4 * 0.5 Ω = 2 Ω.

However, you mentioned that one cell is wrongly connected. If a cell is connected in the opposite direction (negative to positive instead of positive to negative), its emf would subtract from the total emf instead of adding to it. So, if one cell is wrongly connected, the total emf would be 6V - 2 * 1.5V = 3V.

The total internal resistance would remain the same, as it doesn't depend on the direction of the cells. So, the total internal resistance would still be 2 Ω.

Please provide the rest of the question so I can give a more complete answer.