Electricity — Science STD 10 — Question

What is the position of the image when an object is placed at a distance of 20cm from a concave mirror of focal length 20cm?

Which contains more carbon-dixoide: exhaled air or inhaled air? Why?

Give the law of combination of resistances in series.

Draw ray diagrams showing the image formation by a concave mirror when an object is placed:Between focus and centre of curvature of the mirror.

A white powdery substance having strong smell of chlorine is used for disinfecting drinking water supply at waterworks. Identify the substance. Give its chemical name and write the chemical reaction for its preparation.

If the magnification of a body of size 1m is 2, what is the size of the image?

What is meant by the reactivity series of metals? Arrange the following metals in an increasing order of their reactivities towards water:
Zinc, Iron, Magnesium, Sodium

Silver metal does not combine easily with oxygen but silver jewellery tarnishes after some time. How?

An element A has 4 valence electrons in its atom whereas element B has only one valence electron in its atom. The compound formed by A and B does not conduct electricity. What is the nature of chemical bond in the compound formed? Give its electron-dot structure.

Explain why, carbon cannot reduce oxides of sodium or magnesium.