English Medium कक्षा १० - CBSE Important Questions for Science

A student uses a lens of focal length 40 cm and another of –20 cm. Write the nature and power of each lens

A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of correcting it.

Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is 220 V?

Show how would you join three resistors, each of resistance 9 Ω so that the equivalent resistance of the combination is 

1) 13.5 

2) 6 Ω

List the factors on which the resistance of a conductor in the shape of a wire depends.

Why are metals good conductors of electricity whereas glass is a bad conductor of electricity? Give reason?

Why are alloys commonly used in electrical heating devices? Give reason.

State Fleming’s left hand rule.

What is meant by homologous series of carbon compounds?

State the reason why carbon can neither form C⁴⁺ cations nor C⁴⁻ anions but forms covalent compound.

On what factors does the resistance of a conductor depend?

State significance of pollination.

Write one main difference between asexual and sexual mode of reproduction. Which species is likely to have comparatively better chances of survival – the one reproducing asexually or the one reproducing sexually? Give reason to justify your answer.

Define the power of a lens.

What is a solenoid?

Write the name and structural formula of the compound obtained when ethanol is heated at 443 K with excess of conc. H₂SO₄. Also write chemical equation for the reaction stating the role of conc. H₂SO₄ in it.

Give one example of a unisexual flower.

Mention the changes a flower undergoes after fertilisation.

Mention the types of mirrors used as (i) rear view mirrors, (ii) shaving mirrors. List two reasons to justify your answers in each case.

Define the term dispersion of white light.