Various types of measuring tools include:
A Caliper is used to measure the outside, inside, and depth dimensions of objects. It is particularly useful in mechanical and automotive work, where precision is essential.

Draw the pattern of the magnetic field lines for the two parallel straight conductors carrying current of same magnitude 'I' in opposite directions as shown. Show the direction of magnetic field at a point O which is equidistant from the two conductors. (Consider that the conductors are inserted normal to the plane of a rectangular cardboard.)