Consider the following circuit. Meters in the circuit are not ideal

This circuit can be used to determine the resistance $x$if the

In a carbon resistor the colour code is as following

Red Orange Yellow Golden

the resistance of resistor is

Consider the following circuit, the device in the box is not known. When the key is closed, the galvanometer initially gives some deflection but finally it decays to zero

In an experiment of determination of focal length of a lens with the help of optical bench, a student obtained the following curve for convex lens.