Advertisements
Advertisements
प्रश्न
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.
Advertisements
उत्तर
I = 15 A, R = 8 Ω
Rate of heat produced = Power = I2R = (15)2(8) = 1800 J/s
APPEARS IN
संबंधित प्रश्न
Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes?
An electric motor takes 5 amperes current form a 220 volt supply line. Calculate the power of the motor and electric energy consumed by it in 2 hours.
Name two gases which are filled in filament type electric light bulbs.
1Kwh =`( 1 "volt "xx 1 am pere xx.............)/1000`
List the names of three electrical gadgets used in your house. Write their power, voltage ratingand approximate time for which each one is used in a day. Hence find the electrical energyconsumed by each in a day.
An electric kettle is rated 2.5 kW, 250 V. Find the cost of running the kettle for two hours at Rs. 5.40 per unit.
A potential difference of 6 V is applied across a 3 Ω resistor. What is the current flowinq throuqh the circuit?
Write the SI units for:
(a) Electric current
(b) Potential difference
(c) Charge.
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.
State relative advantages and disadvantages of ring system of wiring over the tree system.
An electric heater is rated 220 V, 550 W. Calculate the electrical energy consumed in 3 hours?
State other bigger units of electric power and express them in watt.
How can electric energy consumed by an electric appliance be calculated in kilowatt hour (kWh)?
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 electrical appliance is rated 1500 W, 250 V. This appliance is connected to 250 V mains. Calculate:
(i) the current drawn,
(ii) the electrical energy consumed in 60 hours,
(iii) the cost of electrical energy consumed at Rs. 2.50 per kWh.
The following table gives the electrical appliances used, their power and the average time for which they are used each day in a home. Estimate the monthly electricity bill if the rate is 60 paise per unit.
| Sr.no. | Name | Nos. | Power rating | Time/day |
| 1 | Bulb | 4 | 100 W | 7.5 hr |
| 2 | Fans | 2 | 50 W | 10 hr |
| 3 | T.V. | 1 | 100 W | 2 hr |
| 4 | Iron | 1 | 500 W | 1 hr |
| 5 | Electric stove | 1 | 750 W | 2 hr |
A room has AC run for 5 hours a day at a voltage of 220V. The wiring of the room consists of Cu of 1 mm radius and a length of 10 m. Power consumption per day is 10 commercial units. What fraction of it goes in the joule heating in wires? What would happen if the wiring is made of aluminium of the same dimensions?
`[ρ_(Cu) = 1.7 xx 10_(Ωm)^-8, ρ_(Al) = 2.7 xx 10^-8 Ωm]`
