Question

The power rating of an appliance is 100W -220 V. What does it indicate?. If this bulb is
connected across 110 V, Calculate its power.

Answer 1

Answer:

625 Ω is the resistance of a bulb rated 100w,250v

Explanation:

Voltage rating on bulb = V = 250 Volts

Power rating on the bulb = 100 Watts

Resistance of the bulb:

Answer 2

Answer:

The power consumed by the appliance when it is connected across a 110V would be 25 watts.

Given:

• Initial Power of the appliance, P = 100W
• Initial Potential difference of the appliance, V = 220

Now the appliance is connected across 110V supply. So

• Changed Potential difference of the appliance, V' = 110V
• Changed Power of the appliance = P'

• Resistance of the appliance = R

Solution:

We know that

P = V^2 / R

R = V^2 / P

R = 220V * 220V / 100W

R = 484 Ohms

Also, Resistance remains the same even if the voltage drop is different. So we can say

P' = V'^2 / R

P' = 110V * 110V / 484 Ohms

P' = 25W

The power consumed by the appliance when it is connected across a 110V would be 25 watts.