The number of circles that touch all the straight lines $x+y=4$,$x-y=-2$,and $y=2$ is

In a transformer,the number of turns in primary and secondary are $500$ and $2000$ respectively. If current in primary is $48 \ A$,the current in the secondary is........$A$

When a certain circuit consisting of a constant $emf$ $E$,an inductance $L$,and a resistance $R$ is closed,the current in it increases with time according to curve $1$. After one parameter ($E$,$L$,or $R$) is changed,the increase in current follows curve $2$,when the circuit is closed a second time. Which parameter was changed and in what direction?

The process of removing seed dormancy by mechanically breaking or removing the seed coat is called:

The volume of the tetrahedron formed by the coterminous edges $\vec{a}, \vec{b}, \vec{c}$ is $3$. Then the volume of the parallelepiped formed by the coterminous edges $\vec{a} + \vec{b}, \vec{b} + \vec{c}, \vec{c} + \vec{a}$ is

Which of the following is a natural fiber?