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प्रश्न
How can electric energy consumed by an electric appliance be calculated in kilowatt hour (kWh)?
उत्तर
The electric energy in kWh van be calculated as follows:
Energy in kWh = `("Power" ("in watt") xx "Time"("in hour"))/1000`
or kWh = `("V"("volt") xx "i" ("ampere") xx "t" ("hour"))/1000`
∴ Energy (in kWh) = `"Vit"/1000`
APPEARS IN
संबंधित प्रश्न
State two factors on which the electrical energy consumed by an electrical appliance depends.
An electric kettle connected to the 230 V mains supply draws a current of 10 A. Calculate:
(a) the power of the kettle.
(b) the energy transferred in 1 minute.
Calculate the cost of operating a heater of 500 W for 20 hours at the rate of Rs 3.90 per unit.
The unit for expressing electric power is:
(a) volt
(b) joule
(c) coulomb
(d) watt
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?
Name the physical quality which is measured in
(i) Kw (ii) kWh
Distinguish between kilowatt and kilowatt-hour.
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.
Why does not the heating coil produce any visible light? in an electric stove.
