`AB` and `CD` are two uniform resistance wires of lengths `100 cm` and `80 cm` respectively. The connections are shown in the figure. The cell of emf `5 V` is ideal while the other cell of `E` has internal resistance `2 Omega`. A length of `20 cm` of wire `CD` is balanced by `40 cm` of wire `AB`. Find the emf `E` in volt, if the reading of the ideal ammeter is `2 A`. The other connecting wires have negligible resistance

Answer

6

Explanation

Potential difference across wire `AB=5V`
`:. p.d.` across `40cm` of this wire `=5/100xx40=2V`
`:. p.d.` across `20 cm` of wire `CD=2V`
`:. p.d.` across wire `CD=2/20xx80=8V`
p.d. across `2Omega` resistor `=2xx2=4V`
`:.` emf of the cell `=12V`