Advertisements
Advertisements
Question
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 |
Advertisements
Solution
We first calculate the total kWh consumption of each appliance per day. This is done is below:
(1) Bulbs: kWh consumption =`(4 xx 100)/1000 "kW" xx 7.5 "h" = 3 "kWh"`
(2) Fans: kWh consumption = `2 xx 50/1000 "kW" xx 10 "h" = 1 "kWh"`
(3) T.V. kWh consumption = `1 xx 100/1000 "kW" xx 2 "h" = 0.2 "kWh"`
(4) Iron: kWh consumption = `1 xx 500/1000 "kW" xx "1 h" = "0.5 kWh"`
(5) Electric stove: kWh consumption = `1 xx 750/1000 "kW" xx "2 h" = "1.5 kWh"`
∴ Total kWh consumption per day = (3 + 1 + 0.2 + 0.5 + 1.5) kWh
= 6.2 kWh = 6.2 unit
∴ No. of.units consumed in one month = 6.2 × 30 unit = 186 units
∴ Monthly electricity bill = 186 × 60 paise = Rs. 111.60.
RELATED QUESTIONS
How many joules are there in one kilowatt-hour?
A bulb marked 12 V, 24 W operated on a 12 volt battery for 20 minutes. Calculate:
(i) the current flowing through it, and
(ii) the energy consumed
What is the resistance, under normal working conditions of a 240 V electric lamp rated at 60 W? If two such lamps are connected in series across a 240 V mains supply, explain why each one appears less bright.
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.
Point out two main disadvantages of ‘Tree System’.
Two electric lamps each rating 100 W, 110 V are connected in series to a 220 V power supply and two other electric lamps each of marking 100 W, 220 V are connected in parallel to the same power supply. Will anyone of the two combinations give more light than the other? Give a reason for your answer.
Three 250 W heaters are connected in parallel to a 100 V supply, Calculate the resistance of each heater.
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.
Unit of electric power may also be expressed as:
A conductor of 10 Ω is connected across a 6 V ideal source. The power supplied by the source to the conductor is ______.
