Question

A 40 W bulb is connected to a 200 V supply line. Determine the current flowing in it and resistance of its filament.
If 25% of the total power is radiated as light, then what will be the heat produced per minute?​

Answer 1

Answer:

P=V^2/R

P:Power dissipation in bulb, V:Voltage across bulb, R:Resistance of bulb.

Now, bulb is rated as 40W, 200V. This simply means that the bulb will dissipate 40W of power when 200V is applied across it. Using this data, we can find the resistance of the bulb. So, R=V^2/P.

So, resistance of bulb is 200^2/40=1000 ohms.

Now, when supply voltage is 100V, then power dissipation is V^2/R=100^2/1000= 10W.

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