In positive numbers less than 1, the zeros between the decimal point and a non-zero number are blank significant

Explanation :

Digits that carry meaning which contributes to its measurement resolution are called significant figures.

In positive numbers less than 1, the zeros between the decimal point and a non-zero number are NOT significant.

For example,

In 0.0000208, the zeros before 2 has no significance. Hence, the significant figures are 3 i.e. 2, 0 and 8.

They are not significant.

Explanation:

The significant figures are the figures which are reliable in any measurement.

For example:

The number is 0.007709, the zeros between the decimal point and the first non zero digit, i.e., between decimal point and 2 are not significant. But the zero between the two non zero digit, i.e., between 7 and 9 is significant.

Thus, the number of significant figures are 4.  

iron would move it is magnetic there is a mag field around the current in the wire

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.