List of top Science Questions

Assertion : The peristaltic movements occur all along the gut. Reason (R): The lining of the gut has muscles that contract rhythmically to push the food in regulated manner.
Which of the following is a non-biodegradable pollutant?
Choose the equation of reaction that correctly represents anaerobic respiration in muscles:
Identify the part that controls the closing and opening of the stomatal pore in leaves of plants. Select the correct option.
State Joule's law of heating.
Name the device used for measuring electric current. How is it connected in a circuit ?
How many bulbs of resistance \( 8 \ \Omega \) each should be connected in parallel combination to draw a current of \( 2 \text{ A} \) from a battery of \( 4 \text{ V} \) ?
Define the S.I. unit of electric current.
Conductors of electric toasters and electric iron are made of an alloy rather than a pure metal. Why ?
Due to change in length and area of cross-section of a conductor, resistance of conductor changes while resistivity does not change. Why ?
A person is unable to read a book placed closer than \( 1 \text{ meter} \) from his eyes. Identify the defect of vision in his eyes. Draw the ray diagrams to show the defect of vision and its correction.
Write the preparation of following compounds with balanced chemical equation :
Baking soda
Bleaching powder
Plaster of Paris
Explain chlor-alkali process with chemical equation. Name the products formed at anode and cathode.
Give one example each of electrolytic decomposition and decomposition by sunlight.
Balance the following chemical reaction: \( Pb(NO_3)_2 + KI \longrightarrow PbI_2 + KNO_3 \)
Name the substance oxidised and reduced in the following reaction: \( ZnO + C \longrightarrow Zn + CO \)
Categorise the following based on their nature: \( ZnO, Na_2O, CO_2 \)
What are amphoteric oxides?
Which of the following group is not ‘biodegradable’ ?
Derive the expression for the equivalent resistance of three resistors \( R_1 \), \( R_2 \) and \( R_3 \) connected in parallel combination.
Two lamps 'A' and 'B' of rating 50 W; 220 V and 100 W, 220 V are connected in series combination. Find out the ratio of the resistances (\(R_A : R_B\)) of these lamps.
(a) What is hypermetropia?
(b) Write any one cause of hypermetropia.
(c) With the help of a suitable ray diagram, explain how hypermetropia is corrected?
Describe an activity to show that a current carrying conductor, placed in an external magnetic field experiences a force.
A current carrying straight wire AB is shown in the given diagram. Out of X, Y and Z on which point will the strength of magnetic field be maximum and why?
(a) The resistance of a wire of 0.01 cm radius and 1.0 cm length is \( 7 \, \Omega \).
Calculate its resistivity.
OR
(b) An electric heater is rated 220 V; 11 A. Calculate the power consumed if the heater is operated at 200 V.