Question

A heater coil rated at (1000 W - 200 V) is connected to 110 volt line. What will be the power consumed?

Answer 1

P = V^2/R

If V = 220 V

we have 100 W = 2202/R

R = 2202/100 Ω = 484 Ω.

This is the resistance of the bulb. When V = 110 V

power consumed =V^2/R = 1102 /484 = 25 W.

Answer 2

Concept:

We will use the concept of joules law of heating. Joule’s law is a mathematical description of the rate at which resistance in a circuit converts electric energy into heat energy.

Given:
heater coil rated at (1000 W - 200 V)

Find:

The power consumed when heater coil connected to 110 v line.

Solution:

From Joules law, the heat consumed is P = V²/R

here V is the potential difference and R is the resistance

∴R = V²/P

given, V=200 volt and P=1000W

∴ R = (200)²/1000

       =40Ω

When it is connected to 110 volt line then

P= V²/R

  = (110)²/40

   302.5 watt

Hence 302.5 watt power will be consumed when a heater coil is connected to 110 volt line.

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