Advertisements
Advertisements
Question
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.
Advertisements
Solution
(i) Maximum power of the circuit = (40 × 15) + (100 × 5) + (80 × 5) + (1000 × 1)
= 600 + 500 + 400 + 1000
= 2500 W = 2.5 kW.
(ii) Maximum current capacity = `"Total wattage"/"Voltage of mains" = 2500/220 = 11.36` (or 11.4) A.
(iii) Electrical energy consumed in a week
In 40 W bulbs = `((40 xx 15) xx (4 xx 7))/1000 = 16.8` kWh
In 100 W bulbs = `((100 xx 5) xx (4 xx 7))/1000` = 14 kWh
In 80 W fans = `((80 xx 5) xx (10 xx 7))/1000` = 28 kWh
In 1 kW heater = `((1000 xx 1) xx (2 xx 7))/1000 = 14` kWh
∴ Total electrical energy consumed = 16.8 + 14 + 28 + 14 = 72.8 kWh
(iv) Cost of electricity = 72.8 × 1.25 = Rs. 91
RELATED QUESTIONS
State two factors on which the electrical energy consumed by an electrical appliance depends.
Name the quantity whose unit is kilowatt?
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?
State whether an electric heater will consume more electrical energy or less electrical energy per second when the length of its heating element is reduced. Give reasons for your answer.
What is the current in the circuit shown (Fig. )
The diagram shows a coil connected to a center zero galvanometerG . The galvanometer shows a deflect ion to the right when the north pole N of a powerful magnet is moved to the right as shown .
(i) Explain, why the defelct ion occurs in the galvanometer.
(ii ) State whether th e current in the coil is cl ockwise or anticl ockwise
when viewed from the end P.
(iii ) State th e observation in G when the coil is moved away from north
pole N of the magnet keeping the magnet stationary.
(iv)State the observation in G when both the coil and the magnet are
moved to right at th e same speed .
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.
The average work done by a human heart while it beats once is 0.5 Joule. The power used by heart if it beats 72 times in a minute:
A electric bulb is rate 220 V, 60 W. its electric cell resistance is nearly
