Which of the following material is used in making the core of a moving coil galvanometer?

Options

A. Copper
B. Nickel
C. Iron
D. Both (a) and (b)

Explanation

To determine which material is used in making the core of a moving coil galvanometer, we can follow these steps:

### Step 1: Understand the Function of the Core
The core of a moving coil galvanometer needs to be made of a material that can enhance the magnetic field produced by the coil. This is essential for the sensitivity and accuracy of the galvanometer.

**Hint:** Consider the properties of materials that affect their magnetic behavior.

### Step 2: Compare the Magnetic Susceptibility
We need to compare the magnetic susceptibility of the materials listed: copper, nickel, and iron. Magnetic susceptibility indicates how much a material will become magnetized in an external magnetic field.

- **Copper:** Non-magnetic, very low susceptibility.
- **Nickel:** Ferromagnetic, moderate susceptibility.
- **Iron:** Highly ferromagnetic, very high susceptibility.

**Hint:** Look for materials that can be easily magnetized and have high susceptibility.

### Step 3: Evaluate Initial Permeability
Initial permeability is another important factor. It measures how easily a material can be magnetized.

- **Iron:** Has high initial permeability, making it an excellent choice for the core.
- **Copper and Nickel:** Have lower initial permeability compared to iron.

**Hint:** Remember that higher permeability means better performance in magnetic applications.

### Step 4: Consider Hysteresis Loss
Hysteresis loss refers to the energy loss due to the lag between magnetization and demagnetization of the material. A good core material should have low hysteresis loss to maintain efficiency.

- **Iron:** Generally has low hysteresis loss, making it suitable for use in galvanometers.
- **Copper:** No hysteresis loss as it is non-magnetic.
- **Nickel:** Moderate hysteresis loss.

**Hint:** Think about how energy efficiency is important in the design of sensitive instruments.

### Step 5: Conclusion
Based on the analysis of magnetic susceptibility, initial permeability, and hysteresis loss, we conclude that **iron** is the best material for making the core of a moving coil galvanometer.

**Final Answer:** Iron is used in making the core of a moving coil galvanometer.