Question

a calculate the monthly bill for a heater
of resistance 30ohm used on 220v mains
when its is used daily for one hour at
any cost of 5 rupees per kilowatt hour​

Answer 1

Given:

30 ohm used on 220v mains is used daily for one hour @ 5 rupees per kilowatt hour.

To find:

Total Monthly Bill ?

Calculation:

First , let's find out the net energy used.

$P = \dfrac{ {(voltage)}^{2} }{resistance}$

$\implies \: P = \dfrac{ {(220)}^{2} }{30}$

$\implies \: P = 1613.3 \: watt$

Now, energy E :

$E = P \times t$

$\implies E = 1613.3 \times 1$

$\implies E = 1613.3 \: watt \: hr$

$\implies E = 1.613 \: kw\: hr$

$\implies E = 1.613 \:unit$

So, total energy in 30 days:

$\implies E = 1.613 \:unit \times 30$

$\implies E = 48.39 \:unit$

So, total cost:

= E × (cost per unit)

= 48.39 × 5

= Rs 241.95

So, net cost is Rs 241.95.