Question

If a bulb is rated 40w and 220v find resistance

Answer 1

power = (v*v)/r
40 = (220*220)/r
r = 1210 ohm

Answer 2

Resistance is

The electrical resistance of an object is a measure of its opposition to the flow of electric current.

The inverse quantity is electrical conductance, and is the ease with which an electric current passes.

Electrical resistance shares some conceptual parallels with the notion of mechanical friction.

   

                                    Power = Voltage × Current

first we find current ,

                                   Current  = Power / Voltage

According to question,

        Voltage V = 220 v

         Power P = 40 w

                                  Current  = Power / Voltage

                                   Current  = 40 / 220

                                   Current  = Power / Voltage

                                   Current  = 0.18 A

Now,

                              Resistance = Voltage / Current

                              Resistance = 220 / 0.18

                              Resistance= 1222 Ohms

so,

                         Resistance of the bulb (R) = 1222 Ohms.

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