# An electric iron of 1100 W is operated for 2 hrs daily. What will be the electrical consumption expenses for that in the month of April? (The electric company charges Rs 5 per unit of energy). - Science and Technology 1

Numerical

An electric iron of 1100 W is operated for 2 hrs daily. What will be the electrical consumption expenses for that in the month of April? (The electric company charges Rs 5 per unit of energy).

#### Solution

Electric power required for working of iron, P = 1100 W
Duration for which the iron is operated daily = 2 h = $2 \times 60 \times 60 = 7200 s$

Electric energy consumed by iron in 7200 s is

$E = 1100 \times 7200 = 7920000 J$
Thus, total energy consumed in the month of April,
$E' = E \times 30 = 7920000 \times 30 = 237600000 J$
We know,
1 unit =$3 . 6 \times {10}^6 J$
or, $1 J = \frac{1}{3 . 6 \times {10}^6}$ unit
Thus,
$237600000 J = \frac{237600000}{3 . 6 \times 1000000} = 66$ units
Cost of 1 unit of energy = Rs 5
Thus, total electrical consumption expenses for the month of April = 66 $\times$5 = Rs 330
Concept: Effects of Electric Current - Heating Effect of Electric Current
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