Advertisements
Advertisements
प्रश्न
Define watt-hour. How many joules are equal to 1 watt-hour?
Advertisements
उत्तर
Watt hour is a smaller commercial unit of electric energy, which is spent by an electric appliance of 1 watt power in 1 hour, i.e.
1 watt hour = 1 watt × hour = 1 watt × (60 × 60)s
= 3600 joule.
APPEARS IN
संबंधित प्रश्न
1 kWh = ________ J
A bulb is rated as 250 V; 0.4 A. Find its : (i) power, and (ii) resistance.
Which uses more energy: a 250 W TV set in 1 hour or a 1200 W toaster in 10 minutes?
When an electric lamp is connected to 12 V battery, it draws a current of 0.5 A. The power of the lamp is:
(a) 0.5 W
(b) 6 W
(c) 12 W
(d) 24 W
Why is an electric light bulb not filled with air? Explain why argon or nitrogen is filled in an electric bulb.
An electric heater of resistance 8 Ω takes a current of 15 A from the mains supply line. Calculate the rate at which heat is developed in the heater.
A current of 2 A is passed through a coil of resistance 75Ω for 2 minutes. (a) How much heat energy is produced? (b) How much charge is passed through the resistance?
A bulb of 40 W is used for 12.5 h each day for 30 days. Calculate the electrical energy consumed.
The diagram above shows a circuit with the key k open. Calculate :
(i) the resistance of the circuit when the key k is open.
(ii) the current drawn from the cell when the key k is open.
(iii) the resistance of the circuit when the key k is closed.
(iv) the current drawn from the cell when the key k is closed.
What is wrong with the circuit diagram (Fig. 34)? Carefully check the symbols and assign proper positive and negative signs to them.
Define electric power. An electrical device of resistance R is connected across a source of voltage V and draws a current I. Derive an expression for power in terms of current and resistance.
State three factors on which the heat produced in a metallic wire due to passage of current in it depends.
Why is the heating element of an electric oven wound on a helix? State the reason.
The electric bulbs used these days have a coil-coiled filament. State its reason.
What changes in energy occur in an electric bulb?
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.
Of the three connecting wires in a household circuit: Which two of the three wires are at the same potential? In which of the three wires should the switch be connected?
Why is the electric power from the generating station transmitted at high voltage?
An electric lamp A of 40 W and another electric lamp B of 100 W are connected to 220 V supply. Calculate the ratio of their filament resistances?
An Electric bulb is marked 100 W, 230 V. What how long would this lamp take to consume one unit of electricity?
A bulb is connected to a battery of e.m.f. 6V and internal resistance 2Ω A steady current of 0.5A flows through the bulb. Calculate the resistance of the bulb.
The resistance of filament of an electric heater is 500 Ω It is operated at 200V for 1 hour daily. Calculate the current drawn by the heater and the energy consumed in joule.
The resistance of filament of an electric heater is 500 Ω It is operated at 200V for 1 hour daily. Calculate the current drawn by the heater and the energy consumed in kWh, by the heater in a month of 30 days.
A 100-watt electric bulb is used for 5 hours daily and four 60 watt bulbs are used for 5 hours daily. Calculate the energy consumed (in kWh) in the month of January.
1 mV is equal to:
