List of top Science Questions

(i) Two magnetic field lines do not intersect each other. Why?
(ii) How is a uniform magnetic field in a given region represented?
Draw a diagram in support of your answer.

Assertion (A): Green plants trap only 1% of the energy of sunlight that falls on their leaves. Reason (R): All green plants are the producers in a food chain.

Write the name and formula of
(1) an acidic salt and
(2) a basic salt giving the name of the parent acid and parent base used to form the salt in each case.

The pH of an aqueous solution of a salt is 9. The types of acid and base from which this salt is formed are:

The resistance of a metallic wire of 100 m is 20 \(\Omega\). If the radius of the wire is 5 mm, find the resistivity of the metal of the wire.

(A) (i) Name three techniques/devices used by human females to avoid pregnancy. Mention the side effects caused by each.
(ii) What will happen if in a human female (a) fertilisation takes place, (b) an egg is not fertilised?

OR

(B) (i) Draw a diagram showing spore formation in Rhizopus and label the (a) reproductive and (b) non-reproductive parts. Why does Rhizopus not multiply on a dry slice of bread?
(ii) Name and explain the process by which reproduction takes place in Hydra.

Write the shape of the magnetic field produced by a current carrying straight conductor. State the rule to find the direction of this field.

Study the diagram given below and answer the questions that follow:

(i) Name the defect of vision represented in the diagram. Give reason for your answer.
(ii) List two causes of this defect.
(iii) With the help of a diagram show how this defect of vision is corrected.

“Stability of DNA in a species is ensured during sexual reproduction.” Justify the statement.

One mole of a hydrocarbon, on combustion in air, produces two moles of \( \text{CO}_2 \), two moles of \( \text{H}_2\text{O} \), and a large amount of heat. This hydrocarbon is:

Assertion (A): The rainbow is a natural spectrum of sunlight in the sky.
Reason (R) : Rainbow is formed in the sky when the sun is overhead and water droplets are also present in air.

Which of the following statement(s) is (are) true about human heart?
(a) Right atrium receives oxygenated blood from lungs through pulmonary artery.
(b) Left atrium transfers oxygenated blood to left ventricle which sends it to various parts of the body.
(c) Right atrium receives deoxygenated blood through vena cava from upper and lower body.
(d) Left atrium transfers oxygenated blood to aorta which sends it to different parts of the body.

Give reasons for the following:
(i) Alveoli in lungs are richly supplied with blood capillaries.
(ii) Respiratory pigment in the blood takes up oxygen and not carbon dioxide.
(iii) During anaerobic respiration, a 3-carbon molecule is formed as an end product instead of CO₂ in human beings.
OR
(i) Name the movements that occur all along the gut in human digestive system. How do they help in digestion?
(ii) Where is bile juice stored in human body? List two roles of bile juice.

Mention the pathway of urine starting from the organ of its formation. Name any two substances which are reabsorbed from the initial filtrate in the tubular part of the nephron.

List two functions each of the following parts of the human female reproductive system: (1) oviduct (2) uterus (3) ovary

What is vegetative propagation? Is this process sexual or asexual? Justify your answer.

Select two plants from the following which are obtained by this technique: Banana, Papaya, Jasmine, Mustard

An electrical heater of resistance 10 Ω draws a steady current of 5 A from the service mains for 2 hours. Find the power of this heater and the amount of energy consumed by the heater in kilowatt-hour.

How does the embryo get nourishment inside the mother’s body? Explain briefly.

List three advantages of practising the process/technique by the farmers.

Name and explain the process used to obtain sodium hydroxide from the aqueous solution of sodium chloride (Brine). Name the two gases which are given at the anode and the cathode respectively. List two uses of each of these gases.

What does a food chain represent? “The number of trophic levels in a food chain is limited.” Give an example stating reason to justify this statement.

Is it possible that a trait gets inherited, but not expressed? Give an example to justify your answer.

Name the plant growth hormone which is synthesized at the shoot tip. Explain why the shoot of a potted plant bends towards light coming from a window.

What are decomposers? Explain how the decomposers (i) keep the environment clean, and also (ii) replenish the soil nutrients.