Question 99: Magnetism and Matter

Question

The $$B$$-$$H$$ curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solended with $$1000$$ turns/cm. The current that should be passed in the solended to demagnetise the ferromagnet completely is :

Accepted Answer

Given that,
In the solenoid there is 1000 turns in 1 cm.
$$	herefore\,\,\,\,$$  In 100 cm or 1 m no of turns
= 1000 $$ 	imes $$ 100 = 10
5
turns/m
$$	herefore\,\,\,\,$$ No of turns, n = 10
5
Correctivity of  ferromagnet,  H = 100 A/m
As we know,
H = n I
$$	herefore\,\,\,\,$$ I = $${{100} \over {{{10}^5}}} = 1mA$$
$$	herefore\,\,\,\,$$  Current to demagnetise the ferromagnet = 1 mA.

Answer

$$1$$ $$mA$$

Answer

$$2$$ $$mA$$

Answer

$$20\,\mu A$$

Answer

$$40\,\mu A$$

Magnetism and Matter

The $B-H curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solended with 1000$ turns/cm. The current that should be passed in the solended to demagnetise the ferromagnet completely is :

Choose the correct answer: