Electrical

# Which Bulb Will Glow Brighter (100W) Or (60W)?

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When a 60 W, 200 V bulb is connected in series with a 100 W, 200 V bulb across a 200 V A.C. power supply, which bulb will glow brighter?

60-watt bulb will glow brighter than 100-watt bulb.
Why?
When two bulbs are connected in series across a power supply, the voltage drop across each bulb depends upon its resistance value.
60 Watt power value is less than 100 Watt. This means a 60-watt bulb must have a higher resistance value to resist the current flow.

Let us consider,
Resistance of 60-watt bulb = R1
Resistance of 100-watt bulb = R2
Therefore,     R1  >  R2

We know that,
Voltage drop, V = IR
As R1 is greater than R2, therefore voltage drop across the 60-watt bulb is more than the 100-watt bulb. Hence 60W bulb will consume more power and glow brighter.

In Short, the voltage drop across a 60W bulb is more than 100W because a 60W bulb has higher resistance. Hence 60W bulb will glow brighter.

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