Find the minimum number of cells required to produce a current of `1.5A` through a resistance of `30Omega.` Given that the emf of each cell is `1.5V` and the internal resistance is `1Omega`.

Options

A. 30
B. 120
C. 40
D. 60

Answer

B

Explanation

`i_(max)=(mE)/(2r)=(nE)/(2R)`
`n=` number of cells in each row.
`m=` number of rows
`1.5=(1.5xxm)/(2xx1)`
`m=2`
`therefore` total no of cells, `=nxxm=2xx60=120`