The supply voltage to a room is 120 V. The resistance of the lead wires is 6 . A 60 W bulb is already switched on. What is the decrease of voltage across the bulb, when a 240 W heater is switched on in parallel to the bulb?
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As discussed in
Power dissipiated in external resistance -
Power of heater =
Voltage across bulb before heater switched on
When Heater and bulb in parallel then
Voltage across bulb after heater switched on: