Advertisements
Advertisements
Question
Calculate the cost of operating a heater of 500 W for 20 hours at the rate of Rs 3.90 per unit.
Advertisements
Solution
Power rating of the heater, P = 500 W
Duration of the operation, t = 20 hours
Electrical energy consumed = P x t
= 500 W x 20 hours
= 10000 W = 10 kW
Rate for 1 kW = Rs. 3.90
Total cost of operating = units consumed x rate = 10 x Rs. 3.90 = Rs. 39
APPEARS IN
RELATED QUESTIONS
Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes?
Which one has a higher electrical resistance : a 100 watt bulb or a 60 watt bulb?
Name the quantity whose unit is (i) kilowatt, and (ii) kilowatt-hour.
An electric fan runs from the 230 V mains. The current flowing through it is 0.4 A. At what rate is electrical energy transferred by the fan?
What is meant by "electric power"?
Define kilowatt-hour.
How much energy does a 100 W electric bulb transfer in 1 minute?
(a) 100 J
(b) 600 J
(c) 3600 J
(d) 6000 J
When a current of 4.0 A passes through a certain resistor for 10 minutes, 2.88 × 104 J of heat are produced. Calculate
the power of the resistor.
the voltage across the resistor.
An electric bulb is rated ‘100 W, 250 V’. What information does this convey?
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
When a current I flows through a resistance R for time t, the electrical energy spent is given by:
(a) IRt (b) I²Rt (c) `IR^2t` (d) `I^2R ⁄t`
An electric bulb of resistance 500 Ω draws current 0.4 A from the source. Calculate:
- the power of bulb and
- the potential difference at its end.
An electric current is passed through a metallic wire. The wire gets heated up. Give the reason. Is it possible to melt the wire by passing a heavy current?
Which material is the calorimeter commonly made of? Give one reason for using this material.
State relative advantages and disadvantages of ring system of wiring over the tree system.
At what voltage is the electric power generated at the generating station? Explain the transmission of this power to your house.
I ampere of current is passed through a resistor of resistance R ohm for time t second. Obtain expression for
(i) the electrical energy, and
(ii) the electrical power spent.
An electric bulb is rated as 100W – 250V. What information does it convey? Calculate the resistance of its filament while glowing.
Two bulbs are rated: bulb A 100W, 120 V bulb B 10 W, 120 V. If both are connected across a 120V supply, which bulb will consume more energy, When in parallel? Also calculate the current through each bulb in the above cases.
