The solenoid and the toroid are two pieces of equipment which generate magnetic fields. The synchrotron uses a combination of both to generate the high magnetic fields required. In both, solenoid and toroid, we come across a situation of high symmetry where Ampere's law can be conveniently applied. By long solenoid we mean that the solenoid's length is large compared to its radius. It consists of a long wire wound in the form of a helix where the neighbouring turns are closely spaced. So each turn can be regarded as a circular loop. The net magnetic field is the vector sum of the fields due to all the turns. Enamelled wires are used for winding so that turns are insulated from each other. As the solenoid is made longer it appears like a long cylindrical metal sheet. The field outside the solenoid approaches zero. We shall assume that the field outside is zero. The field inside becomes everywhere parallel to the axis. Consider a rectangular Amperían loop abcd. Along cd the field is zero as argued above. Along transverse sections bc and ad, the field component is zero. Thus, these two sections make no contribution. The direction of the field is given by the right-hand rule. The solenoid is commonly used to obtain a uniform magnetic field.
Which of the following generates magnetic field?

Options

A. Solenoid
B. Toroid
C. Both solenoid and toroid
D. None of the above

Explanation

To solve the question regarding which equipment generates a magnetic field, we can follow these steps:

### Step 1: Understand the Equipment
We need to identify the two pieces of equipment mentioned in the question: the solenoid and the toroid.

### Step 2: Analyze the Properties of Each Equipment
- **Solenoid**: A solenoid is a long coil of wire that generates a magnetic field when an electric current passes through it. The magnetic field inside a long solenoid is uniform and parallel to its axis, while the field outside is negligible.

- **Toroid**: A toroid is a circular coil of wire, shaped like a doughnut. Similar to a solenoid, when an electric current flows through the wire, it generates a magnetic field. The magnetic field inside the toroid is also uniform, and outside the toroid, the magnetic field is negligible.

### Step 3: Apply Ampere's Law
Both the solenoid and toroid exhibit high symmetry, allowing us to apply Ampere's Law effectively. This law states that the magnetic field in a closed loop is proportional to the electric current passing through it.

### Step 4: Determine the Magnetic Field Generation
From the analysis, we conclude that both the solenoid and the toroid generate magnetic fields when an electric current flows through them.

### Step 5: Select the Correct Option
Based on the information provided, the correct answer to the question "Which of the following generates magnetic field?" is:
- **Both solenoid and toroid**.

### Final Answer
The correct option is **C: Both solenoid and toroid**.

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