Equal number of identical cells are joined first in series and then in parallel in a circuit with resistance R to send a current through it. Under what condition, the currents in both the cases will be the same.

Explanation

Suppose, emf of each of the n number of identical cells=e and internal resistance =r.
When the cells are connected in series and current is allowed to flow through the resistance R, the magnitude of current is given by,
`I_1=(n e)/(R+nr)`
Again, connecting the cells in parallel we get a current through R, given by,
`I_2=(n e)/(nR+r)`
According the question `I_1=I_2`
So, `R+nr=nR+ror,R(1-n)=r(1-n)or,R=r`
So if the resistance of the circuit is equal to the internal resistance of each cell, then in both the cases the current will be the same.