What direction compass needle points at poles ? Which needle to be used at poles ?

What happens to compass needles at the Earth's poles ?

Magnetic field lines show the direction (at every point) along which a small magnetised needle aligns (at the point). Do the magnetic field lines also represent the lines of force on a moving charged particle at every point ?

What is poling?

A child staying in a coastal region tests the drinking water and also the sea water with his tester. He finds that compass needle deflects more in the case of sea water. Can you explain the reason?

The direction of current flowing in a coil is shown in the figure. What type of magnetic pole is formed at the face that has flow of current as shown in the figure?

Two vertical poles 20m and 80m heigh stand apart on a horizontal plane. The height of the point of intersection of the lines joining the top of each pole to the foot of the other is

Figure 9.34 shows an equiconvex lens (of refractive index 1.50) in contact with a liquid layer on top of a plane mirror. A small needle with its tip on the principal axis is moved along the axis until its inverted image is found at the position of the needle. The distance of the needle from the lens is measured to be 45.0cm. The liquid is removed and the experiment is repeated. The new distance is measured to be 30.0cm. What is the refractive index of the liquid?

An electrician wants to repair an electric connection on a pole of height 9m. He needs to reach 1.8 m below the top of the pole to do repair work. What should be the length of the ladder which he should use, when he climbs it at an angle of 60^(@) with the ground? What will be the distance between foot of the ladder and foot of the pole?