Liquid in C is most acidic, followed by that in A and B. Greater the acidic strength, smaller is the pH value. Hence pH value of liquid in B is more than that in A and C.
Liquid in C is most acidic, followed by that in A and B. Greater the acidic strength, smaller is the pH value. Hence pH value of liquid in B is more than that in A and C.
Electrical resistance of a conductor is a measure of the opposition offered by it for flow of electric charge through it. Mathematically, resistance is given as: Resistance R = Potential difference across the conductor V/Current I SI unit of resistance is ohm Ω. Resistance of a conductor is said toRead more
Electrical resistance of a conductor is a measure of the opposition offered by it for flow of electric charge through it. Mathematically, resistance is given as:
Resistance R = Potential difference across the conductor V/Current I
SI unit of resistance is ohm Ω. Resistance of a conductor is said to be 1 Ω, if a potential difference of 1 volt is to be applied across its ends to maintain a flow of 1 ampere of current. The resistance R of a conductor is (a) directly proportional to its length L, (b) inversely proportional to its cross-section area A, and (c) depends on the nature of the material of the conductor. Thus,
R ∝ L/a or R = pl = pL/A,
where p is a constant depending upon the nature of the material of conductor and is known as its resistivity.
(i) The resistance of a wire is doubled if its length is double keeping other factors unchanged. It is because R ∝ L.
(ii) If radius of wire is doubled then its cross-section area (A =πr²) becomes 4 times of its original value. Since R ∝ 1/A hence the new resistance of wire becomes 1/4 th, of its original value.
(a) Three common features of respiratory organs of animals : (i) Animals absorbs oxygen from water or air hence have a structure that increases the surface area which is in contact with the oxygen rich atmosphere. (ii) Since exchange of oxygen-carbon dioxide has to take place across this surface, itRead more
(a) Three common features of respiratory organs of animals :
(i) Animals absorbs oxygen from water or air hence have a structure that increases the surface area which is in contact with the oxygen rich atmosphere.
(ii) Since exchange of oxygen-carbon dioxide has to take place across this surface, it is very fine and delicate.
(iii) ln order to protect this surface, it is placed within the body, so there are passages that take air to this area.
(b) Differences between aerobic and anaerobic respiration:
Aerobic respiration:-
(i) Oxygen is used to breakdown glucose.
(ii) Glucose is broken down completely to release large amount of energy.
Anaerobic respiration:-
(i) Do not involve oxygen to breakdown glucose.
(ii) Breakdown of glucose is incomplete to release small amount of energy.
(a) The soil B with pH 4.5 is acidic. To neutralise this soil, it is treated with powdered chalk (CaCO₃). Acids react with chalk to form calcium salt. This reaction will neutralise the acidity of the salt. (b) Ant's sting and nettle leaf sting inject formic acid (methanoic acid) into the skin of a pRead more
(a) The soil B with pH 4.5 is acidic. To neutralise this soil, it is treated with powdered chalk (CaCO₃). Acids react with chalk to form calcium salt. This reaction will neutralise the acidity of the salt.
(b) Ant’s sting and nettle leaf sting inject formic acid (methanoic acid) into the skin of a person. The effect of the sting can be neutralised by rubbrng with some alkaline substance like sodium bicarbonate or sodium carbonate.
(c) Aquatic animals are used to live in river water with a definite pH range. Whenever there is a change in the pH of water, it endangers the life of these organisms.
A student took 5 mL of lemon Juice in each of test tubes A, B and C. She added 5 mL of water in A and 20 mL of water in B. She tested for pH value in all the three tubes. She would find that pH value of liquid :
Liquid in C is most acidic, followed by that in A and B. Greater the acidic strength, smaller is the pH value. Hence pH value of liquid in B is more than that in A and C.
Liquid in C is most acidic, followed by that in A and B. Greater the acidic strength, smaller is the pH value. Hence pH value of liquid in B is more than that in A and C.
See lessThe first colour on the colour chart of pH ship from the top is :
(a) The colour chart starts from red and ends in violet.
(a) The colour chart starts from red and ends in violet.
See lessWhat is meant by resistance of a conductor? Name and define its SI unit. List the factors on which the resistance of a conductor depends. How is the resistance of a wire affected if: (i) its length is doubled, (ii) its radius is doubled?
Electrical resistance of a conductor is a measure of the opposition offered by it for flow of electric charge through it. Mathematically, resistance is given as: Resistance R = Potential difference across the conductor V/Current I SI unit of resistance is ohm Ω. Resistance of a conductor is said toRead more
Electrical resistance of a conductor is a measure of the opposition offered by it for flow of electric charge through it. Mathematically, resistance is given as:
Resistance R = Potential difference across the conductor V/Current I
SI unit of resistance is ohm Ω. Resistance of a conductor is said to be 1 Ω, if a potential difference of 1 volt is to be applied across its ends to maintain a flow of 1 ampere of current. The resistance R of a conductor is (a) directly proportional to its length L, (b) inversely proportional to its cross-section area A, and (c) depends on the nature of the material of the conductor. Thus,
R ∝ L/a or R = pl = pL/A,
See lesswhere p is a constant depending upon the nature of the material of conductor and is known as its resistivity.
(i) The resistance of a wire is doubled if its length is double keeping other factors unchanged. It is because R ∝ L.
(ii) If radius of wire is doubled then its cross-section area (A =πr²) becomes 4 times of its original value. Since R ∝ 1/A hence the new resistance of wire becomes 1/4 th, of its original value.
(a) State three common features of respiratory organs of animals. (b) Write two points of difference between aerobic respiration and anaerobic respiration.
(a) Three common features of respiratory organs of animals : (i) Animals absorbs oxygen from water or air hence have a structure that increases the surface area which is in contact with the oxygen rich atmosphere. (ii) Since exchange of oxygen-carbon dioxide has to take place across this surface, itRead more
(a) Three common features of respiratory organs of animals :
See less(i) Animals absorbs oxygen from water or air hence have a structure that increases the surface area which is in contact with the oxygen rich atmosphere.
(ii) Since exchange of oxygen-carbon dioxide has to take place across this surface, it is very fine and delicate.
(iii) ln order to protect this surface, it is placed within the body, so there are passages that take air to this area.
(b) Differences between aerobic and anaerobic respiration:
Aerobic respiration:-
(i) Oxygen is used to breakdown glucose.
(ii) Glucose is broken down completely to release large amount of energy.
Anaerobic respiration:-
(i) Do not involve oxygen to breakdown glucose.
(ii) Breakdown of glucose is incomplete to release small amount of energy.
(a) The pH of soil Ais7.5 while that of soil B is 4.5. Which of the two soils A or B should be treated with powdered chalk to adjust its pH and why? (b) Name the chemical which is injected into the skin of a person: (i) During an ant’s sting. (ii) During the nettle leaf sting. How can the effect of these stings be neutralised? (c) Explain how the pH change in the river water can endanger the lives of aquatic animals like fish?
(a) The soil B with pH 4.5 is acidic. To neutralise this soil, it is treated with powdered chalk (CaCO₃). Acids react with chalk to form calcium salt. This reaction will neutralise the acidity of the salt. (b) Ant's sting and nettle leaf sting inject formic acid (methanoic acid) into the skin of a pRead more
(a) The soil B with pH 4.5 is acidic. To neutralise this soil, it is treated with powdered chalk (CaCO₃). Acids react with chalk to form calcium salt. This reaction will neutralise the acidity of the salt.
See less(b) Ant’s sting and nettle leaf sting inject formic acid (methanoic acid) into the skin of a person. The effect of the sting can be neutralised by rubbrng with some alkaline substance like sodium bicarbonate or sodium carbonate.
(c) Aquatic animals are used to live in river water with a definite pH range. Whenever there is a change in the pH of water, it endangers the life of these organisms.