In the case of bar magnet, lines of magnetic induction

Explanation

The correct answer is that lines of magnetic induction run continuously through the bar and outside. Magnetic field lines form closed loops, indicating that they do not have a beginning or an end. Outside the magnet, they travel from the north pole to the south pole, while inside, they continue from the south pole back to the north pole. This continuous loop structure is fundamental to understanding magnetic fields. Option A is incorrect because it suggests that field lines start and end at the poles, which is misleading. Option C is incorrect as it suggests emergence in circular paths from the middle, which does not happen. Option D is incorrect because it implies that field lines are only produced at the north pole, which is not true, as they form loops.