Physics Circle home Student Login

Home›Chapters›Magnetic Properties of Materials PYQs›Hysteresis, Soft Iron vs Steel & Shielding›Question 15

JEE Main 2018 (15 Apr, Shift 1) · Hysteresis, Soft Iron vs Steel & Shielding

Hysteresis, Soft Iron vs Steel & Shielding question from JEE Main 2018 (15 Apr, Shift 1)

Q15JEE Main 2018 · 15 APR · SHIFT 1Medium

Hysteresis, Soft Iron vs Steel & Shielding

The B-HB\text{-}H curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solenoid with 10001000 turns/cm. The current that should be passed in the solenoid to demagnetise the ferromagnet completely is:

Figure

Show answer and solution

Answer: (a)

  1. From the graph, the loop cuts the HH-axis at H=100 A/mH = 100\text{ A/m}. This is the coercivity, the field needed to demagnetise the ferromagnet.
  2. n=1000 turns/cm=105 m−1n = 1000\text{ turns/cm} = 10^{5}\text{ m}^{-1}
  3. I=Hn=100105=10−3 AI = \dfrac{H}{n} = \dfrac{100}{10^{5}} = 10^{-3}\text{ A}
  4. So the answer is (a) 1 mA.
Report a mistake

More questions on Hysteresis, Soft Iron vs Steel & Shielding