Question

Which has greater resistance 1kw electric heater or a 100w filament bulb both marked for 220v?

Answer 1

Answer:-

Filament of bulb.

Given:-

Rating of electric heater = ( 1 kw, 220 v)

Rating of bulb = ( 100 w, 220 v)

To find :-

Which has greater resistance.

Solution :-

1 kw = 1000 w

The relation of power, voltage and resistance is given by formula :-

$\boxed{\sf{P = \dfrac{v^2}{R}}}$

Put the value,

Resistance of electric heater = $R _1= \dfrac {(220)^2}{1000}$

$\implies$ $R_1 = \dfrac {48400}{1000}$

$\implies$ $R _1= 48.4 ohm$

hence,resistance of electric heater is $\48.4 ohm$

Now,

Resistance of filament of bulb:-

$\implies$ $R_2= \dfrac {(220)^2}{100}$

$\implies$ $R_2= \dfrac {48400}{100}$

$\implies$ $R_2 = 484 ohm$

We can see that $R_1 < R_2$

hence,resistance of filament of bulb is more than resistance of electric heater.

Without solving question we can also tell which has greater resistance.

From given formula,

$P \propto \dfrac{1}{R}$

I. e, If P > then R is lesser.

Or, If P < then R is greater.

here, P of electric heater is > than power of bulb So, the electric heater has lesser resistance.

Answer 2

Answer:

Electric heater

Explanation: