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.)
Find the mean and mode of the following data:
| Class | 15--20 | 20--25 | 25--30 | 30--35 | 35--40 | 40--45 |
| Frequency | 12 | 10 | 15 | 11 | 7 | 5 |