An electric lamp which runs at 80 volt d.c. and consumes 10 ampere is connected to 100 volt, 50 Hz a.c. mains. Calculate the inductance of the choke required.

Answer

`16 Omega`

Explanation

Resistance of lamp, `R = (V)/(I)=(80)/(10) = 8 Omega`
In order to use an arc lamp with operating `240 V` a resistance `R` is to be connected in series with it so that the current in the circuit should not excted `10A` then
`V = I (R + R') or 240 = 10(8 + R')`
or `R' = 24 - 8 = 16 Omega`