Question

What effect will there on the magnetic compass when it is brought near a current carrying solenoid ?
1. The needle of the compass will rest in the direction of the magnetic field due to solenoid at that point
2. The needle rests opposite to the direction of the magnetic field due to solenoid at that point.
3. None of the above
4. Cannot say

Answer 1

Hint: A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents and magnetic materials .A charge that is moving in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field .
Solenoid : it is a generic term for a coil of wire used as an electromagnet . It also refers to any device that converts electrical energy to mechanical energy using a solenoid .The device which creates a magnetic field from electric and uses the magnetic field to create linear motion .

Complete solution:
A current carrying solenoid will act as a bar magnet having north and south polarity .Magnetic field lines originate from the north pole and terminate to south pole . Like shown in the given figure :
When the compass with its north pole is brought near the north pole of the solenoid ,the needle deflects towards the west that is away from the north pole of the solenoid because like poles repel each other .
Thus ,the needle of the compass will rest in the direction of the magnetic field due to
solenoid at that point

Therefore, option 1 is correct.

Note:
Direction of the north and south pole in a solenoid can be determined by using Fleming’s thumb rule. When fingers curl in the direction of current and thumb point upward or downward according to the curling fingers ,the direction of thumb gives us the direction of flux as upwards or downwards. The point from where flux is coming out acts as the north pole and the other one as south pole.