Question

Which among the following is made of soft iron?
A. Permanent magnet
B. Electromagnet
C. Temporary magnet
D. All

Answer 1

Understand what soft iron is and its properties. Then check for each option. Check the properties of each option one by one specially their magnetic properties and compare them with the properties of soft iron and then select the answer which best fits with the properties of soft iron.

Complete answer:
First let us understand the meaning of soft iron.Soft iron is the type of iron which can be easily magnetized when there is an inducing magnetic field and is demagnetized when the inducing magnetic field is removed. In other words we can say soft iron has high susceptibility and low retentivity. Now let us check the options one by one.

Option A: - Permanent magnets are magnets which have their own magnetic field, the magnetic field is generated from the interior of the objects. When an external magnetic field is applied it may be attracted or repelled by the magnetic field generated from a permanent magnet but when the external magnetic field is removed, it will still have its own magnetic field. So, permanent magnets cannot be made of soft iron.

Option B: - An electromagnet consists of a wire which is wound into a coil and inside the coil lies a metal core. When electric current passes through the coil it generates a magnetic field as moving charge generates a magnetic field, this magnetic field induces a magnetic field in the metal core and when the current stops flowing the induced magnetic field also vanishes. Thus, compared with the definition of soft iron, we can say the metal core inside the coil is a soft iron. Therefore, option (B) is correct.

Option C: - Temporary magnets can act like permanent magnets when it is placed in a strong magnetic field and loses its magnetism when the external field is removed. It is somehow similar to the properties of soft iron but in case of temporary magnets any kind of soft metals can be used and in the case of electromagnets only soft iron is used.

So, the proper answer would be electromagnets.

Hence, the correct answer is option B.

Note: Iron can be classified into two forms, that is, hard iron and soft iron. The properties of soft iron are discussed in the above question. Hard irons are the type of iron which cannot be easily magnetized or demagnetized, they act like permanent magnets.