Advertisements
Advertisements
Question
State two advantages of filling an inert gas in an evacuated electric filament lamp.
Advertisements
Solution
(i) The inert gas is filled at very low pressure to prevent oxidation as well as evaporation and thus increases its life.
(ii) While bulb is working, a convection current is set-up within it which carries the spurting particles of tungsten upward towards the cap and hence the blackening of the lower part (transparent portion) of the bulb is avoided.
RELATED QUESTIONS
1kWh = …….. J
Calculate the current through a 60 W lamp rated for 250 V. If the line voltage falls to 200 V, how is the power consumed by the bulb affected?
An electric toaster draws 8 A current in a 220 V circuit. It is used for 2 h. Find the cost of
operating the toaster if the cost of electrical energy is Rs. 4.50 per kWh.
A bulb with rating 250 V, 100 W is connected to a power supply of 220 V situated 10 m away using a copper wire of area of cross-section 5 mm2. How much power will be consumed by the connecting wires? Resistivity of copper = 1.7 × 10−8 Ωm
Tick(✓) the correct choice in the following:
In the circuit shown in the following fig, the e.m.f. of the cell is 4 volts, the current
flowing through the resistor is
Which cable, one rated 15A and the other rated 5A will be thicker? Give a reason.
Why is heating coil wound in the form of a helix in electric stove?
Out of the three fuses with current ratings 5A, 10A, 15A, which one is to be connected in a geyser circuit marked 3 kW, 220V? Give reason for your answer.
A electric bulb is rate 220 V, 60 W. its electric cell resistance is nearly
