There is a magnetic material of coercitivy `2xx10^(3)Am^(-1)`. What current should flow through solenoid of length 15 cm having 150 turns to demagnetise the substance completely?

Options

A. `4A`
B. `2.5A`
C. `2A`
D. `3.5A`

Answer

To solve the problem, we need to determine the current that should flow through a solenoid to demagnetize a magnetic material given its coercivity.

### Step-by-Step Solution:

1. **Identify Given Values:**
- Coercivity (H) = \(2 \times 10^3 \, \text{A/m}\)
- Length of the solenoid (L) = 15 cm = \(15 \times 10^{-2} \, \text{m} = 0.15 \, \text{m}\)
- Number of turns (N) = 150 turns

2. **Calculate the Number of Turns per Unit Length (n):**
\[ n = \frac{N}{L} = \frac{150}{0.15} = 1000 \, \text{turns/m} \]

3. **Use the Relationship Between Magnetic Intensity (H), Number of Turns per Unit Length (n), and Current (I):**
The relationship is given by:
\[ H = n \cdot I \]
Rearranging this to find the current (I):
\[ I = \frac{H}{n} \]

4. **Substitute the Values into the Equation:**
\[ I = \frac{2 \times 10^3 \, \text{A/m}}{1000 \, \text{turns/m}} = 2 \, \text{A} \]

5. **Conclusion:**
The current that should flow through the solenoid to demagnetize the substance completely is **2 A**.