Advertisements
Advertisements
Question
Two lamps are rated 220V, 50W and the other rated 220V, 100W are connected in series with the mains of 220 V. Explain, why the 50W lamp glows more?
Advertisements
Solution
From relation R = V2/P, the resistance of filament of 50W lamp will be more than that of 100W lamp. If the two lamps are connected in series with the mains, same current will flow through each lamp. From relation H = I2Rt, since resistance of 50W lamp is more than that of 100W lamp, so the 50 W lamp will consume more electrical energy than that of 100W lamp, in the same time. Hence the 50W lamp will glow more.
RELATED QUESTIONS
Define Electric power.
State the S.I. unit of electrical power.
A bulb marked 12 V, 24 W operated on a 12 volt battery for 20 minutes. Calculate:
(i) the current flowing through it, and
(ii) the energy consumed
An electric kettle is rated 2.5 kW, 250 V. Find the cost of running the kettle for two hours at Rs. 5.40 per unit.
Name the physical quantity which is measured in kW.
Name three main characteristics of an heating element.
The electric bulbs used these days have a coil-coiled filament. State its reason.
Three 250 W heaters are connected in parallel to a 100 V supply, Calculate the resistance of each heater.
Find the cost of operating an electric toaster for two hours if it draws 8 A current on a 110 volt circuit. The cost of electrical energy is Rs. 2.50 per kWh.
