The figure shows a long solenoid, a cylindrical coil of a number of turns of insulated copper wire, connected to a battery through an ammeter A and a rheostat Rh.
(i) Which end of the solenoid is an N-pole and which end is an S-pole?
(ii) Draw the magnetic field lines inside the solenoid and indicate their directions. Are magnetic field lines closed?
(iii) How can you increase the strength of the magnetic field inside the solenoid? Give two methods.
i. Point P is the South pole and point Q is the North pole because of the specified direction of the current flowing in the solenoid and by using right-hand thumb rule our thumb points towards point Q, so it is North pole.
ii. Yes, magnetic field lines form closed loops and inside the solenoid they go from south to north pole and outside the solenoid it goes from north to south pole.
iii. By looking at the formula for magnetic field of solenoid we can say the two methods for increasing magnetic field are:–
B = μon I
a) By increasing the number of turns per unit length.
b) By increasing the amount of current passing through it.