Four identical cells each of emf 2V, are joined in parallel providing supply of current to external circuit consisting of two `15 Omega` resistors joined in parallel. The terminal voltage of the cells ae read by an ideal voltmeter is 1.6V. Calculate the internal resistance of each cell.

Explanation

Total internal resistance of the combination `r_(eq)=(r)/(4)`
Total e.m.f. `E_(eq)=2V`
Total external resistance `R=(15xx15)/(15+15)=(15)/(2)=7.5Omega`
Current drawn from equivalent cell `I=("terminal potential")/("external resistance")=(1.6 )/(7.5)A`
`because E-I((r)/(4))=1.6 therefore 2-(1.6)/(7.5)((r)/(4))=1.6`
`rArr r=7.5Omega`