Question

a 220 v, 100w bulb is connected to a source of 180v. The power consumed by the bulb is nearly...

Answer 1

We know that the bulb acts like a resistor or a load to the circuit.

Now we will make use of Ohm's law which says:

$V=I \times R$, where 'V' is the voltage across the circuit, 'I' is the current in the circuit, and 'R' is the resistance.

We also know that the power across a load is given by:

$P= V \times I=VI$, putting $I=\frac{V}{R}$, we get:

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

Now, the 100 watt bulb operates at 220 volts

We can find the resistance of the bulb by plugging the values of voltage and power:

$R=\frac{220^2}{100} =484$ ohms

So the resistance of the bulb is 484 ohms.

When the bulb operates at 180 volts, the power consumed is:

$P=\frac{V^2}{R} =\frac{180^2}{484} =66.94$

So, the power consumed by the bulb is 66.94 watts when operated at 180 volts.