please explain me....magnetic field lines are normal to the magnetic surface

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AB is a current carrying conductor in the plane of the paper as shown in the figure below. (i) What is the direction of the magnetic field produced by it at point ‘X’? Write the statement of the rule used to find the direction of field lines. (ii) If the polarity of the battery connected to the wire is reversed, how would the direction of the magnetic field be changed? (iii) Point ‘X’ is at a distance r1 and point ‘Y’ is at a distance r2 (r1

formula of c in curies temperature please ansewr i am waiting for the answer

 

Describe in operation electro dynamic whattmetermeter

For minimum flux the angle between the magnetic field and normal to the surface is