The strength of magnetic field of an electromagnet is increased by inserting a core of ...............

Explanation

To solve the question "The strength of magnetic field of an electromagnet is increased by inserting a core of ...............", we can follow these steps:

### Step 1: Understand the Concept of Electromagnets
An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. The strength of the magnetic field can be influenced by various factors, including the material used in the core.

**Hint:** Remember that electromagnets rely on electric current to generate a magnetic field.

### Step 2: Identify the Role of the Core Material
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