Answer : The resistance of the bulb is 4.5 ohms
Solution :
Using ohm's law,
[tex]V=I\times R\\\\R=\frac{V}{I}[/tex]
where,
V = applied voltage = 1.8 volts
I = current = 0.4 amperes
R = resistance
Now put all the given values in the above formula, we get the resistance of the bulb.
[tex]R=\frac{1.8V}{0.4A}=4.5\Omega[/tex]
Therefore, the resistance of the bulb is 4.5 ohms