Question

The cold resistance of a certain gas filled tungsten lamp is 18.2 Ω and its hot

resistance at the operating voltage of 110 v is 202 Ω find the current

1) at the instant of switching on

2) The normal working current.​

Answer 1

1) current at the instant when light turned on = 6.04 Amp

2) if the voltage is 202 Ω then current I = 0.544 Amp or if it is 20.2 Ω then current I = 5.44 Amp

1) lets assume that at the instance when we turn on the switch the resistance is cold resistance (r) = 18.2 Ω

operating voltage (v) = 110 v

current I = v/r

I = 110 v/ 18.2 Ω

I = 6.04 Amp

2) the normal working current if the resistance is 20.2 Ω  then I = 5.44 Amp

if it is 202 Ω  then I = 0.544 Amp