Question

E. Answer the following in detail.
1. Describe the directive property of a magnet.
2. How will you test if a given metallic bar is a magnet or not?
3. List the properties of magnetic lines of force.
4. How is the single-touch method of magnetism different from the double-touch method?
5. How can you make an electromagnet? What is the material used for the core of an electromagnet?
6. Differentiate between a temporary magnet and a permanent magnet.​

Answer 1

Answer:

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1) Suspend a bar magnet freely . Note the direction in which it comes to rest. It always comes to rest along the north- south direction of the earth. This is termed as the directive property of a magnet.

2) Bring one pole of a bar magnet ( say the north pole ) close to both the ends of the substance , one by one . If one end is attracted and the other end is repelled , the given substance is a magnet. If both ends are attracted , the given substance is not a magnet. Repulsion is the true test of magnetization.

3) The magnetic lines of force has the following properties:

• Each line is a closed and continuous curve.
• They originate from the north pole and terminate at the south pole.
• They will never intersect each other.
• They are crowded near the poles where the magnetic field is strong.

4) The method of making an artificial magnet by rubbing a permanent magnet over it, in the same direction, is known single touch method whereas double touch method is a method of magnetizing a material by using two magnets instead of one.

5) A simple electromagnet consisting of a coil of wire wrapped around an iron core. A core of ferromagnetic material like iron serves to increase the magnetic field created. The strength of magnetic field generated is proportional to the amount of current through the winding.

6) A permanent magnet is one that retains its magnetic properties for a long period of time. ... Temporary magnets are those that simply act like permanent magnets when they are within a strong magnetic field. Unlike permanent magnets however, they loose their magnetism when the field disappears.