Question

A room heater is rating 500 w 220v find the resistance of coil

Answer 1

Given,

Rating of the room heater = 500 W

Potential difference across the heater = 220 V

The power rating of an electric appliance is the electrical energy consumed per second by the appliance when connected across the marked voltage of the mains.

P = $\frac{V^{2}}{R}$

on putting the values,

$500 = \frac{220*220}{R}$

$R = \frac{220*220}{500}$

R =  22* 22 / 5

R = 484 / 5

R = 96.8 ohm.

Thus, the resistance of the coil is 96.8 Ohm.

Answer 2

Answer: 96.8 Ω

Explanation:

Given,

P  = 500 W

Voltage (V) = 220 Volt

Resistance of the coil (R) = ?

We know that,

For any circuit,

P = Vi × cosФ

Where Ф is phase difference between V and i.

Since, this heater is treated as pure ohm's circuit. Therefore Ф=0

cosФ = cos0° = 1

So,

P = Vi

Again using ohm's law,

Putting i = V/R

P = V²/R

500 = (220×220)/R

R = (220×220)/500

R = (22×22)/5

R = 484/5

R = 96.8 Ω