Advertisements
Advertisements
प्रश्न
The coil of an electric bulb takes 40 watts to start glowing. If more than 40 W are supplied, 60% of the extra power is converted into light and the remaining into heat. The bulb consumes 100 W at 220 V. Find the percentage drop in the light intensity at a point if the supply voltage changes from 220 V to 200 V.
उत्तर
Case-I : When the supply voltage is 220 V.
Power consumed by the bulb = 100 W
Excess power = 100 − 40 = 60 W
Power converted to light = 60% of 60 W = 36 W
Case-II : When the supply voltage is 200 V.
Power consumed = \[\frac{200}{220} \times 100= 82.64 W\]
Excess power = 82.64 − 40 = 42.64 W
Power converted to light = 60% of 42.64 W = 25.584 W
Percentage drop in light intensity,
\[p = \frac{36 - 25 . 584}{36} \times 100\]
\[ \Rightarrow p = 28 . 93 \approx 29 %\]
APPEARS IN
संबंधित प्रश्न
An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.
At what frequency is AC supplied to residential houses?
Which one has a higher electrical resistance : a 100 watt bulb or a 60 watt bulb?
An electric bulb is rated at 220 V, 100 W. What is its resistance?
How much energy does a 100 W electric bulb transfer in 1 minute?
(a) 100 J
(b) 600 J
(c) 3600 J
(d) 6000 J
State the S.I. unit of electrical power.
An electric bulb is rated ‘100 W, 250 V’. What information does this convey?
Define 1 kilowatt hour.
Write the SI units for:
(a) Electric current
(b) Potential difference
(c) Charge.
Two resistors A and B of 4 Ω and 6 Ω, respectively are connected in parallel. The combination is connected across a 6 volt battery of negligible resistance. Calculate the power dissipated in each resistor.
What is the order of current drawn by appliances connected to the ‘light circuit’ of a household?
How does the heat produced by die passage of current in a metallic wire depend on the resistance of the wire.
Establish the relation that heat produced in a metallic conductor due to the flow of current is V2t/R joules, where V is the potential difference across the ends of the conductor, R its resistance and t is the time in second for which current flows.
An electric bulb is rated as 100W – 250V. What information does it convey? Calculate the current through the filament of the bulb.
An electric appliance is rated at 1000 W, 250V. Calculate:
(i) The electrical energy consumed by the appliance in 12 hour.
(ii) The cost of energy consumed at Rs. 1.20 per kWh.
How long would this appliance take to use 1 kWh energy when operated at 250 V?
A family uses 8 kW of power. Direct solar energy is incident on the horizontal surface at an average rate of 200 W per square meter. If 20% of this energy can be converted to useful electrical energy, how large an area is needed to supply 8 kW?
A conductor of 10 Ω is connected across a 6 V ideal source. The power supplied by the source to the conductor is ______.
1 kWh = ______ J.
