Advertisements
Advertisements
प्रश्न
Name the quantity whose unit is (i) kilowatt, and (ii) kilowatt-hour.
उत्तर
(i) Kilowatt is the unit of power.
(ii) Kilowatt-hour is the unit of energy.
APPEARS IN
संबंधित प्रश्न
Explain why, filament type electric bulbs are not power efficient.
Write the SI units for:
(a) Electric current
(b) Potential difference
(c) Charge.
Fig . shows the essent ial features of a battery operated bell. The hammer strikes the gong when the swi tch is closed . State and explain the effect of using the following material successively to form the core.
(a) Plastic
(b) Steel
(c) Copper
Water in an electric kettle connected to a 220 V supply took 5 minutes to reach its boiling point. How long will it take if the supply voltage falls to 200 V?
What changes in energy occur in an electric heater?
An electric filament lamp is connected to a supply of voltage higher than the recommended value. Give reasons, why compared with a normal performance, the lamp emits a brighter light and its life is shortened.
How is the amount of heat produced calculated due to the passage of current in a metallic conductor? Derive an expression for it.
A bulb is marked 100W, 220V and an electric heater is marked 2000 W, 220 V.
(i) What is the ratio between the resistances of these two devices?
(ii) How does the power-voltage rating of a device help us to decide about the type of leads (connecting wires) to be used for it?
(iii) In which of the above two devices, a thicker connecting wire of lead is required?
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.
