Tag: magnetic compass

The north pole of the normal magnet points in the north direction of the earth. Thus north direction is found first with the help of the magnet..

A freely suspended magnet always points in the north south direction as earth behaves as large magnet. the north pole of the earth's magnet attracts the south pole of the magnet and vice versa.

The compass needle acts as a freely suspended magnet which points in north-south direction under the influence of earth's magnetic field lines. So, a small plotting compass can be used to plot a magnetic field.

When a magnetic compass is brought close to a current carrying wire there is deflection in the compass due to the formation of magnetic field. The magnetic field lines around a long wire which carries an electric current form concentric circles around the wire. The direction of the magnetic field is perpendicular to the wire. 
The deflection increases when the current is increased because the magnitude of the field is directly proportional to the strength of the electric current. That is, stronger the electric field, stronger the magnetic field.

The N-pole of a compass points to the S pole of a permanent magnet. Since apposite pole always attracts.

we know,
The time period of vibration magnetometer is,
$T = 2\pi \sqrt {\dfrac{1}{{mH}}} $
For some moment of inertia $I$ and magnetic moment $m$
$T \propto \dfrac{1}{{\sqrt H }}$
T can be reduced if horizontal component of earth's magnetic field $H$ is increased. But
$H = R\cos \theta $
$H$ is high if the dip is zero.
This occurs at the equator.
Hence the period can be reduced by moving towards the equator.

Here, $H _E = 0.16G = 0.16 \times 10^{-4}T$, dip angle $(\delta) = 60^0$
Then, magnitude of earth's field.
$B _E = \dfrac{H _E}{cos \delta} = \dfrac{0.16 \times 10^{-4}}{cos 60^0} T \Rightarrow B _E = \dfrac{0.16 \times 10^{-4}}{1/2} = 0.32 \times 10^{-4}T = 0.32G$

Properties of magnetic lines of force
(i) they always start from north pole and end at the south pole of the magnet outside the magnet.
(ii) they never intersect each other.

In a compass, needle points toward earth's magnetization south thus it its tip is north and its other end is south which is repelled by south pole of other magnet.

A magnetic compass points north because all magnets have two poles, a north pole and a south pole, and the north pole of one magnet is attracted to the south pole of another magnet. 
When this magnetic compass is brought near a magnetic substance, there is change in the direction of the needle based on the polarity of the magnetic substance closer to it. Whereas for a non magnetic substance it is not so.
Hence, the direction in which a compass needle points will distinguish between a magnetic material and a non-magnetic material.