Import Question JSON

Current Question (ID: 16914)

Question:

$\text{A bar magnet has coercivity } 4 \times 10^3 \text{ Am}^{-1}. \text{ It is desired to demagnetize it by inserting it inside a solenoid } 12 \text{ cm long and having } 60 \text{ turns. The current that should be sent through the solenoid is:}$ $1.\ 2 \text{ A}$ $2.\ 4 \text{ A}$ $3.\ 6 \text{ A}$ $4.\ 8 \text{ A}$

Options:

1. $2 \text{ A}$
2. $4 \text{ A}$
3. $6 \text{ A}$
4. $8 \text{ A}$

Solution:

$\text{The bar magnet coercivity } 4 \times 10^3 \text{ Am}^{-1} \text{ i.e., it requires a magnetic intensity } H = 4 \times 10^3 \text{ Am}^{-1} \text{ to get demagnetized.}$ $\text{Let } i \text{ be the current carried by solenoid having } n \text{ number of turns per metre length, then by definition } H = ni. \text{ Here } H = 4 \times 10^3 \text{ Amp turn metre}^{-1}$ $n = \frac{N}{l} = \frac{60}{0.12} = 500 \text{ turn/m}$ $\Rightarrow i = \frac{H}{n} = \frac{4 \times 10^3}{500} = 8.0 \text{ A}$

Import JSON File

Upload a JSON file containing LaTeX/MathJax formatted question, options, and solution.

Expected JSON Format:

{
  "question": "The mass of carbon present in 0.5 mole of $\\mathrm{K}_4[\\mathrm{Fe(CN)}_6]$ is:",
  "options": [
    {
      "id": 1,
      "text": "1.8 g"
    },
    {
      "id": 2,
      "text": "18 g"
    },
    {
      "id": 3,
      "text": "3.6 g"
    },
    {
      "id": 4,
      "text": "36 g"
    }
  ],
  "solution": "\\begin{align}\n&\\text{Hint: Mole concept}\\\\\n&1 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\text{ moles of carbon atom}\\\\\n&0.5 \\text{ mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6] = 6 \\times 0.5 \\text{ mol} = 3 \\text{ mol}\\\\\n&1 \\text{ mol of carbon} = 12 \\text{ g}\\\\\n&3 \\text{ mol carbon} = 12 \\times 3 = 36 \\text{ g}\\\\\n&\\text{Hence, 36 g mass of carbon present in 0.5 mole of } \\mathrm{K}_4[\\mathrm{Fe(CN)}_6].\n\\end{align}",
  "correct_answer": 4
}