Commercial electric motors do not use:

Options

A. An electromagnet to rotate the armature
B. Effectively large number of turns of conducting wire in the current carrying coil
C. A permanent magnet to rotate the armature
D. A soft iron core on which the coil is wound

Explanation

To solve the question "Commercial electric motors do not use:", we will analyze each option provided and determine which one is not utilized in commercial electric motors.

### Step-by-Step Solution:

1. **Understand the Components of Electric Motors**:
Electric motors typically consist of a coil of wire (armature), a magnetic field, and a core material. The interaction between the magnetic field and the current in the coil produces motion.

2. **Evaluate Option A**:
If the option states that electric motors use a large number of turns of conducting wire in the current-carrying coil, this is true. More turns increase the magnetic field strength.

3. **Evaluate Option B**:
If the option mentions that electric motors use a permanent magnet to rotate the armature, this is false. Commercial electric motors primarily use electromagnets rather than permanent magnets for the rotating part.

4. **Evaluate Option C**:
If the option states that electric motors use a soft iron core on which the coil is wound, this is true. The soft iron core enhances the magnetic field produced by the coil.

5. **Identify the Correct Answer**:
Since option B is the only statement that is false (commercial electric motors do not use permanent magnets for rotation), this is the correct answer to the question.

### Final Answer:
Commercial electric motors do not use **permanent magnets** to rotate the armature.

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