Question

Three identical bulbks are connected in parallel with a battery 4.5 v....If the wattage of each bulb is 1.5 watt how much reading will the ammeter a show when all the three bylbs glow simultaneously

Answer 1

Let the three bulbs be r1, r2, r3.

we know that V=4.5V and P=1.5W

we also know that the bulbs are connected in parallel the voltage for all the bulbs will be same as potential difference remains same in parallel,

now from the formula P=V²/R..

we will calculate the resistances of the bulbs

r1=V²/P,r1=20.25/1.5=13.5Ω

likewise we get r2=r3=13.5

now total resistance of the circuit will be R

1/R=1/r1+1/r2+1/r3       therefore    R=4.5Ω

now from the formula V=IR

I=V/R=4.5/4.5=1A

therefore the current reading of the ammeter will be 1A.