Question

Five bulb each having 100w power are used for 4hrs, a heater having 1500w power is used 2 hrs and an electric iron of power 1000 w is used for 5 hrs for 30 days. (i) Calculate the total energy consumed by them. (ii) Convert the Energy into joules

Answer 1

Answer:

(I) 10 KWH

(ii) 36 × 10⁶

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Answer 2

Given,

5 bulbs each having 100W power are used for 4hrs.

A heater having 1500W power is used 2 hrs.

An electric iron of power 1000W is used for 5 hrs.

All the appliances are used for 30 days.

To find,

(i) The total energy consumed by them

(ii) The energy equivalent in Joules

Solution,

We can simply solve this numerical problem by using the following process:

Mathematically,

Power (P) = Energy consumed (E) ÷ Time (T)

=> Energy consumed (E) = Power (P) x Time (T)

Now,

Total units of energy consumed in one day by each bulb = Power (P) x Time (T)

= 100 W x 4 hours

= 400 Wh = 0.4 kWh = 0.4 electrical units

(Since 1 kWh = 1 electrical unit)

So, total units of energy consumed in 30 days by all 5 bulbs

= 0.4 electrical units × 30 days × 5 bulbs

= 60 electrical units

And,

Total units of energy consumed in one day by the heater = Power (P) x Time (T)

= 1500 W x 2 hours

= 3000 Wh = 3 kWh = 3 electrical units

(Since 1 kWh = 1 electrical unit)

So, total units of energy consumed in 30 days by the heater

= 3 electrical units × 30 days

= 90 electrical units

Also,

Total units of energy consumed in one day by the electric iron = Power (P) x Time (T)

= 1000 W x 5 hours

= 5000 Wh = 5 kWh = 5 electrical units

(Since 1 kWh = 1 electrical unit)

So, total units of energy consumed in 30 days by the electric iron

= 5 electrical units × 30 days

= 150 electrical units

So, the total energy consumed by them

= (total units of energy consumed in 30 days by all 5 bulbs) + (total units of energy consumed in 30 days by the heater) + (total units of energy consumed in 30 days by the electric iron)

= 60 electrical units + 90 electrical units + 150 electrical units

= 300 electrical units

Now,

The energy equivalent in Joules

= 300 electrical units × 3600000 Joules

{Since 1 electrical unit = 3600000 Joules}

= (36×3) × 10^7 J

= 108 × 10^7 J

Hence, the total energy consumed is equal to 300 electrical units, that is equivalent to 108 × 10^7 J.