Question

An electric heater of resistance 8 ohm draws 15A from the service mains in 2 hours. Calculate the rate at which heat is developed in the heater.

Answer 1

$\large\bf\underline {To \: find:-}$

• We need to find the rate at which heat is developed in the heater.

$\large\bf\underline{Given:-}$

• resistance of heater = 8 Ω
• current in heater = 15A
• time = 2 hours = 7200second

$\huge\bf\underline{Solution:-}$

▶ we know that ,

• p = VI

By Ohm's law V = IR

So,

• ⚘ p = I²R

where

• p = power
• I = current
• R = Resistance

Now,

Resistance of heater is 8ohm draws 15A current .

➻ p = 15² × 8

➻ p = 225 × 8

➻ p = 1800 w

Hence,

the rate at which heat is developed in the heater is 1800w.

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⚡Power:-

The rate of doing work is known as power.

⚘SI unit of power is watt (w).

• p = VI
• p = I²R
• p = Work done/Time taken

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