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प्रश्न
A house is provided with 15 bulbs of 40W, 5 bulbs of 100W, 5 fans of 80 W, and one heater of 1.0 kW. Each day bulbs are used for 4h, fans for lOh, and heater for 2h. The voltage of mains is 220 V. Calculate:
(i) Maximum power of the circuit in the house,
(ii) maximum current capacity of the main fuse in the house,
(iii) the electrical energy consumed in a week,
(iv) cost of electricity consumed at 1.25 Rs. per kWh.
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उत्तर
(i) Maximum power of the circuit = (40 × 15) + (100 × 5) + (80 × 5) + (1000 × 1)
= 600 + 500 + 400 + 1000
= 2500 W = 2.5 kW.
(ii) Maximum current capacity = `"Total wattage"/"Voltage of mains" = 2500/220 = 11.36` (or 11.4) A.
(iii) Electrical energy consumed in a week
In 40 W bulbs = `((40 xx 15) xx (4 xx 7))/1000 = 16.8` kWh
In 100 W bulbs = `((100 xx 5) xx (4 xx 7))/1000` = 14 kWh
In 80 W fans = `((80 xx 5) xx (10 xx 7))/1000` = 28 kWh
In 1 kW heater = `((1000 xx 1) xx (2 xx 7))/1000 = 14` kWh
∴ Total electrical energy consumed = 16.8 + 14 + 28 + 14 = 72.8 kWh
(iv) Cost of electricity = 72.8 × 1.25 = Rs. 91
संबंधित प्रश्न
An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be ______.
An electric lamp is labelled 12 V, 36 W. This indicates that it should be used with a 12 V supply. What other information does the label provide?
The diagram below shows a circuit containing a lamp L, a voltmeter and an ammeter,. The voltmeter reading 3 V and the ammeter reading is 0.5 A.
What is the resistance of the lamp?
What is the power of the lamp?
The table below shows the current in three different electrical appliances when connected to the 240 V mains supply:
| Appliance | Current |
| Kettle | 8.5 A |
| Lamp | 0.4 A |
| toaster | 4.8 A |
- Which appliance has the greatest electrical resistance? How does the data show this?
- The lamp is connected to the main supply by using a thin, twin-cored cable consisting of live and natural wires. State two reasons why this cable should not be used for connecting the kettle to the mains supply.
- Calculate the power rating of the kettle when it is operated from the 240 V mains supply.
- A main takes the kettle abroad where the mains supply is 120 V. What is the current is the kettle when it is operated from the 120 V supply?
Electrical power P is given by the expression P = (Q × V) ÷ time. What do the symbols Q and V represent?
Two lamps, one rated 220 V, 50 W and the other rated 220 V, 100 W, are connected in serieswith mains of 220 V. Explain why does the 50 W lamp consume more power
With reference to the diagram shown below calculate:
(i) The equivalent resistance between P and Q.
(ii) The reading of ammeter.
(iii) The electrical power between P and Q.
A student wants to use an electric heater, an electric bulb and an electric fan simultaneously.
How should these gadgets be connected with the mains? Justify your answer giving three reasons.
