Explain how will you make a tester for testing electric current using a magnetic compass and empty matchbox, a battery of two cells and connecting wire?

Yor are provided with a magnetic compass, an empty match box, a battery of two cells and connecting wires. Using these objects how will you make a tester for testing an electric circuit? Draw the necessary circuit diagram and explain.

Arrange the following steps in sequential order to demonstrate the magnetic effect of the elctric cur-rent using magnetic compass. (A) Wind an insulated conducting wire around the magnetic compass such that the axis of the coil is directed along east west direction and con-nect the free ends of the wire to a cell through a switch. (B) Take a magnetic compass. (C ) When current flows through the conducting wire, it behaves as a magnet and deflects the compass needle. (D) When the switch is closed, the magnetic nee-dle in the compass deflects from its initial posi-tion and when the switch is opend, the needle comes back to its initial position.

How can you make a potentiometer of given wire length more sensitive using a resistance box?