State two differences between an electromagnet and a permanent magnet.

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State two differences between an electromagnet and a permanent magnet.

Class 10 | Electro Magnetism | ICSE | Physics | Selina

State two differences between an electromagnet and a permanent magnet.

Solution:

Electromagnet	Permanent magnet
It is composed of soft iron	It is composed of steel
Its polarity can be reversed	Its polarity cannot be reversed.

Also, the Electromagnets’ magnetic strength can be increased or lowered. But this is not possible with permanent magnets. Electromagnets have a higher magnetic power than permanent magnets. Electromagnets are more widely used than permanent magnets because of these advantages.

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More Material

A …… lens is used to correct myopia and a ….. lens is used to correct hypermetropia.
A Concave, concave
B Convex, convex
C Convex, concave
D Concave, convex

Rate of reaction of any substance depends on
(A) active mass
(B) molecular weight
(C) atomic weight
(D) equivalent weight

Formula of oleum is
(A) $\mathrm{H}_{2} \mathrm{~S}_{2} \mathrm{O}_{7}$
(B) $\mathrm{H}_{2} \mathrm{SO}_{4}$
(C) $\mathrm{H}_{2} \mathrm{SO}_{3}$
(D) $\mathrm{H}_{2} \mathrm{SO}_{5}$

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If $A(-2,0), B(0,4)$ and $C(0, k)$ be three points such that area of a $A B C$ is 4 sq units, find the value of $k$ .

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Find the value of $k$ for which the points $A(1,-1), B(2, k)$ and $C(4,5)$ are collinear.

Find the value of $k$ for which the points $P(5,5), Q(k, 1)$ and $R(11,7)$ are collinear.

Find the value of $k$ for which the points $A(3,-2), B(k, 2)$ and $C(8,8)$ are collinear.

Use determinants to show that the following points are collinear. $P(-2,5), Q(-6,-7)$ and $R(-5,-4)$

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