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Could somebody explain to me why in a series circuit with 3 lights one at 4.2w , 60w and 50w only the 4.2W lamp will light up I understand that the current will be the same through out but I am a little confused thank you
You haven't stated the voltage, but let's go with 230 V.
The rating will be at 230 V.
W = VI so for the 4.2 W lamp, I = 18 mA. R = V/I = 230/0.018 = 12.6 kΩ.
For the 50 W lamp, I = 0.22 A and R = 1060 Ω.
For thé 60 W lamp, I = 0.26 A and R = 880 Ω.
Total resistance = 14.5 kΩ.
Current through the series = 16 mA. W = I²R. So the 4.2 W lamp draws 3.2 W, which is enough to illuminate it. The 50 W lamp uses only 0.27 W, so it gets a bit warm and does not glow. The 60 W lamp gets 0.23 W, which is even worse.
