Answer:
Explanation:
The static charges are generated due to excess or deficiency of electrons, because these are the smallest quanta of charge available at the molecular level which can get transferred with minimal energy requirement.
These charges are usually generated by friction between the two surfaces leading to the transfer of electron from one to another.
When a plastic pipe is rubbed with a cloth then due to friction the surface of the cloth loses electron which gets stuck at the surface of the pipe making it negatively charged.
Answer:
80%
Explanation:
Efficiency of machine = work output/work input ×100 %
From question, work output = 20J
Work input = 25J.
Therefore efficiency = 20/25 × 100 %
Efficiency = 20×4 %
Efficiency = 80%
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1) Focal length
We can find the focal length of the mirror by using the mirror equation:
(1)
where
f is the focal length
is the distance of the object from the mirror
is the distance of the image from the mirror
In this case,
, while
(the distance of the image should be taken as negative, because the image is to the right (behind) of the mirror, so it is virtual). If we use these data inside (1), we find the focal length of the mirror:
from which we find
2) The mirror is convex: in fact, for the sign convention, a concave mirror has positive focal length while a convex mirror has negative focal length. In this case, the focal length is negative, so the mirror is convex.
3) The image is virtual, because it is behind the mirror and in fact we have taken its distance from the mirror as negative.
4) The radius of curvature of a mirror is twice its focal length, so for the mirror in our problem the radius of curvature is: