(a) Since two \(8\Omega \) resistors are in parallel, their effective resistance (\({ R }_{ P }\)) is given by,
\(\frac { 1 }{ { R }_{ P } } =\frac { 1 }{ 8 } +\frac { 1 }{ 8 } +\frac { 1 }{ 4 } \) or \({ R }_{ P }=4\Omega \)
(b) Total resistance in the circuit
\(R=4\Omega +{ R }_{ P }=4\Omega +4\Omega =84\Omega \)
Current through the electric circuit
\(I=\frac { V }{ R } =\frac { 8V }{ 8\Omega } =1A\)
(c) The potential difference \(4\Omega \) resistor V
 I \(=IR=1\times 4=4V\) 
(d) Power dissipated in \(​​​​4\Omega \) resistor P=\({ (I) }^{ 2 }\)
\(R={ (1) }^{ 2 }(4)=4W\)
(e) There is no difference in the readings of ammeters \({ A }_{ 1 }\) and  \({ A }_{ 2 }\) as same current flows through all elements in a series circuit.

Compound with molecular formula C₂H₄O₂ should be Ethanoic acid reacts with Na metal to give sodium ethanoate.
\(\underset{\underset{Ethanoic\ acid}{(C)}}{2CH_3COOH}+2Na\rightarrow\underset{\underset{Sodium\ ethanoate}{(R)}}{2CH_3COONa}+H_2\)
\(\underset{\underset{Ethanoic\ acid}{(C)}}{CH_3COOH}+\underset{\underset{methanol}{(A)}}{CH_3OH}\xrightarrow{conc. H_2SO_4}\underset{\underset{Methyl\ acetate}{(S)}}{CH_3COOCH_3+H_2O}\)
\(CH_3COOH+\underset{Sodium\\ hydroxide}{NAOH}\rightarrow\underset{\underset{Sodium\ ethanoate}{(R)}}{CH_3COONa}+H_2O\)
\(\underset{\underset{Methyl\ acetate}{(s)}}{CH_3COOCH_3}+NaOH\rightarrow\underset{\underset{sodium\ ethanoate}{(R)}}{CH_3COONa}+\underset{\underset{Method}{(A)}}{CH_3OH}\)

(a) When we magnetise a piece of magnetic material such as soft iron by keeping it inside a coil and then passing current through it, the magnet so formed is called electromagnet.
(b) (i) Steel is used to make permanent magnet.
(ii) Soft iron is used to make temporary magnets.
(c) Take a coil of wire having N number of turns and then wound it around a soft iron core. Connect the end of the wire with a battery and plug key and then let current pass through the coil. While current is passing through the coil, bring a compass near the coil. It will be observed that compass needle shows deflection. This shows that the coil will have a magnetic field of its own. The magnet so formed is called an electromagnet.

Since the element B belongs to atomic number 17, it must be chlorine.
The element which burns golden flame in air is sodium. Therefore, the element A must be sodium.
When element sodium and chlorine reacts, it forms sodium chloride, the compound C. The compound C on electrolysis gives sodium hydroxide and hydrogen gas.
Thus, A = Na; B = CI₂; C = NaCI; D = NaOH.
         Chemical Reactions involved:
              \(2Na+{ CI }_{ 2 }\rightarrow 2NaCI\)
\(2NaCI(aq)+{ 2H }_{ 2 }O(I)\rightarrow 2NaOH(aq)+{ CI }_{ 2 }(g)+{ H }_{ 2 }(g)\)

The alimentary canal is nearly 9 m long. It includes -
1. Mouth and Buccal Cavity: It is the upper most opening of human digestive system which gives passage if for ingestion of food. Buccal cavity takes in the food cuts the food into small pieces and chews them to make it soft or easy swallowing. Buccal cavity also has three pairs of salivary glands. These glands secrete saliva
which contains water, salts, mucin and an enzyme ptyalin. Ptyalin is salivary amylase which splits starch and glycogen into maltose.
2. Pharynx: It acts as a passage for the food from buccal cavity to oesophagus.
3. Oesophagus: It is a long and tubular structure which pushes the food rhythmically forward.
4. Stomach: It is a large organ which expands when food enters it. It serves four functions:
(i) Storage of food - Carbohydrates gets digested till the salivary enzyme ptyalin is destroyed by HCI, secreted in the stomach.
(ii) Churning of food - The stomach wall produces muscular contraction, for the food to get churned and to mix it thoroughly with gastric juice.
(iii) Partial digestion - There are three types of gastric juice in stomach namely HCI, protein digesting enzyme (pepsin) and mucus.
(iv) Exit of food - The stomach releases food into the small intestine in a controlled and regulated manner.
Functions of the Gastric Juices
(i) HCI - Makes the tnedium acidic, kills the germs present in the food.
(ii) Pepsin - Acts in acidic medium, breaks proteins into peptone.
(iii) Mucus - Protects the inner lining of the stomach from the action of the acid under normal conditions.
(iv) Gastric juice - Also contains some gastric lipase which partially breaks down lipids.
(v) Regulation of flow of food - Stomach regulates the flow of partially digested food into the small intestine.
5. Small intestine: It is the longest part of digestive system. It is a narrow tube divided into three parts 
(i) duodenum
(ii) jejunum and 
(iii) ileum. It is the site of the complete digestion of proteins, carbohydrate and fats. Duodenum receives the secretion of bile from bile duct and pancreatic juice from pancreatic duct.
Bile juice
(i) It is secreted by liver and stored temporarily in the gall bladder.
(ii) It has bile pigments and bile salts.
(iii) It has no enzymes and thus has no chemical action on food, but breaks down the fat molecules into small globules.
(iv) This process is called emulsification of fats. Pancreatic juice
(i) It includes pancreatic amylase which breaks down starch, pancreatic lipase which breakdown lipids and trypsin for digesting proteins.
(ii) The secretions of pancreatic duct make the medium alkaline, which is favourable for the action of pancreatic enzymes.
Pancreas secretes hormones insulin and glucagons. The walls of small intestine contains glands which secrete intestinal juice called succus entericus which helps in digesting protein A into amino acids, carbohydrates into glucose, fats into fatty acids and glycerol. The digested food is taken up by the walls of the intestine which has numerous fingers like projection called villi. Villi are richly supplied with blood vessels which the absorbed food to obtain energy. The presence of villi and
blood capillaries increases the capacity of absorption by the wall of intestine
6. Large intestine: It includes three parts namely caecum, colon and rectum. It is shorter but wider than small intestine. It secretes mucus for lubrication. The undigested food is collected as faeces egested out through anus which is regulated by anal sphincter.

Various plant hormones and their effects are as follows:
(i) Auxin : Promotes cell elongation and thus promotes growth of a plant part.
(ii) Gibberellins : Promotes growth.
(iii) Cytokinin :  Promotes cell division and thus promotes growth.
(iv) Abscissic acid : Inhibits growth and is responsible for shedding or older parts.

(a) Concentrated sulphuric acid is called the king of chemicals as it is a very strong acid and is highly corrosive.

(b) The three chemical reactions that take place during the conversion of sulfur dioxide to sulphuric acid in the 'Contact Process' are given below.

Step I: Sulphur dioxide is mixed with air and passed over vanadiumpent (V) oxide catalyst heated to \(450^oC\) to form sulphur trioxide.

\(\underset{Sulphur\ dioxide}{2SO_{2(g)}}+\underset{Oxygen}{O_{2(g)}}\underset{\rightleftharpoons }{V_2O_5}\underset{Sulphur\ trioxide}{2SO_{3(g)}}+Heat\)

Step II : Sulphur trioxide is dissolved in concentrated sulphuric acid to form a thick fuming liquid called oleum.

\(\underset{Sulphuric\ acid}{H_2SO_4(l)}+\underset{Sulphur\ trioxide}{SO_{3(g)}}\begin{matrix} V_2O_5 \\ \rightleftharpoons \\ \end{matrix}\underset{Oleum}{H_2S_2O_{7(l)}}\)

Step III: Oleum is diluted with a calculated quantity of water to obtain sulphuric acid.

\(H_2S_2O_{7(l)}+\underset{Water}{H_2O_{(l)}}\rightarrow\underset{Sulphuric\ acid}{2H_2SO_{4(aq)}}\)

(c) If water is added to sulphuric acid then a large amount of heat is evolved.  This changes water to steam, which can splash the acid.  Hence, it is dangerous.

(a) Zinc sulphate and copper is formed when zinc reacts with copper sulphate,
\(\underset{Zinc}{Zn( s)} + \underset{Copper\ sulphate}{CuSO_4} (aq) \rightarrow \underset{Zinc\ sulphate}{ZnSO_4(aq)} + \underset{Copper}{Cu}\)
(b) Hydrochloric acid forms aluminium chloride and hydrogen gas when reacts with aluminium metal.
\(2AI + 6HCI\rightarrow 2AlCl_3 + 3H_2\)
(c) When silver metal is added to copper sulphate solution, no reaction takes place because silver is less reactive than copper

Hydrogen gas is usually liberated when an acid reacts with metal.
e.g. Zn(s) + H₂SO₄ (aq) \(\rightarrow\) ZnSO₄(aq) + H₂ \(\uparrow\)
Test for H₂ gas Testing of H₂ gas presence can be done by passing the gas through soap solution and then bringing a burning splinter near the soap bubble filled with the gas. If the gas burns with a pop sound, it confirms hydrogen.

X. Sodium bicarbonate (NaHCO₃)

Difference in :
(i) Molecular mass = 14 a.m.u. 
(ii) Number of atoms of elements = CH₂

C₄H₁₀ and C₅H₁₂

Manganese or Magnesium.

Hydrogen gas is formed. Bring a burning matchstick near to it, H₂ will burn explosively with 'pop' sound.

In a physical change, no new substance is formed. In a chemical change, new substance is formed.

Reaction of an acid with a metal:
When an acid reacts with a metal, it forms a salt.
Hydrogen which is in all the acids gets displaced and liberated as hydrogen gas.
Acids + Metals \(\rightarrow\) Salt + Hydrogen gas

(a) It is because it has 7 valence electrons. It can gain one electron to form negative ion.So, it is a non-metal.
(b) 'C' has more number of shells than A. So, it is larger in size.
(c) 'B' has one valence electron. It can lose one electron to become stable. So, its valency is equal to 1.

(i) Next homologue of C₂H₄ is C₃H₆
(i) Next homologue of C₄H₆ is C₅H_8.

Michael Faraday in 1831 discovered that mechanical motion can produce current.

The magnetic field lines around a straight conductor carrying current are concentric circles.

Xylem is the tissue which transports water and minerals in plants.

As soon as a piece of sodium metal is dropped into water, bubbles will come out showing the evolution of a gas is hydrogen. The reaction that takes place between sodium metal and cold water is given below :
2Na        +   2H₂O       →  2NaOH          +  H₂
Sodium    Water(cold) Sodium hydroxide Hydrogen

(a) A fuse helps in protecting that appliance from potential damage which may happen due to overload. A fuse wire works because of its lower melting point which is possible because of its respective rating.
(b) If a fuse with larger rating is used with an appliance, the fuse wire shall not melt and hence would fail to serve the required purpose. Due to this, a fuse with defined rating should not be replaced by one with a larger rating.

The uriniferous tubule, or nephron, is the kidney's excretory unit.
Excretion is the process in which an organism's hazardous waste is removed from its body.
The nephron is the fundamental unit of homeostasis, as it is controls the amount of water, ions and other substances in the blood.
Nephron's key tasks include blood filtration, reabsorption, secretion, and urine production.

Translocation

The blood circulation in human heart is called double circulation because the blood passes through the heart twice in one complete cycle of the body-once through the right half in the form of deoxygenated blood and once through the left half in the form of oxygenated blood.

Acid rains are most likely expected in industrial areas where there is emission of oxides of nitrogen and sulphur.

The part of the hindbrain that takes part in the regulation of respiration is medulla oblongata.

Pancreas. It secretes hormones and digestive enzymes.

Neurons are the functional units of the nervous system. They carry the information from the brain and the spinal cord to the different parts of the body and form the different parts of the body to the brain or the spinal cord.

(i) Electric power is related to voltage and electric current as:
Power= Voltage x Current
It is given that the rating of the electric iron is 750W, 220V.
Let the current passing through the bulb be I.
Therefore, 
750=220 x I
I=\(\frac{750}{220}\)=3.41A
Therefore, 3.41A current passes through the electric iron.
It is given that the rating of the electric bulb is 750W,220 V
Therefore, P=\(\frac { { V }^{ 2 } }{ P } \)=\(\frac { { 220 }^{ 2 } }{ 750 } \)=64.53\(\Omega \) when in use.
(ii) Electric power is related to voltage and resistance as:
\(\frac { { \left( Voltage \right) }^{ 2 } }{ Resistance } \)
That is,
P=\(\frac { { V }^{ 2 } }{ R } \)
=64.53\(\Omega \)

Coulomb

The resistance of 25 W lamp bulb has a higher value as compound to that of 50 W lamp bulb. Resistance of the 25 W lamp bulb. Resistance of the 25 W lamp bulb will be double of that of the 50 W lamp bulb.

The S.I. unit od electric potential is volt. It is denoted by V.(Volt)

Rust is the hydrated iron (III) oxide, Fe₂O₃.xH₂O.

(i) Na₂CO₃(s) + 2HCl(aq) \(\longrightarrow \) 2NaCI(aq) + H₂O(I) + CO₂(g)
(ii) CaO(s) + H₂O(I) \(\longrightarrow \)Ca(OH)₂(aq) + Heat
(iii) Pb(NO₃)₂(aq) + NaCl(aq) \(\longrightarrow \) PbCI₂(s) + 2NaNO₃(aq)

The colour changes from yellow to reddish brown. l Soap is basic in nature and the colour of turmeric changes from yellow to reddish brown in basic medium. The stain turns yellow again.

Reaction in which a single reactant breaks down to give simpler products.
Thermal decomposition-
\(CaCO_{ 2 }\overset { \triangle }{ \longrightarrow } CaO+C{ O }_{ 2 }\)
(Or any other)
Electrolytic decomposition-
2H₂O\(\overset { Electric\quad current }{ \rightarrow } \) 2H₂+O₂
(or)
In a decomposition reaction, a single reactant breaks down into two or more simpler products.
When a decomposition reaction is carried out by heating, it is called thermal decomposition reaction.
\(\underset { (Calucium\quad carbonate) }{ CaCO_{ 3 }(s) } \overset { Heat }{ \rightarrow } \underset { Calcium\quad oxide) }{ CaO(s) } +\underset { (Carbon\quad dioxide) }{ { CO }_{ 2 }(g) } \)
When a decomposition reaction is carried out with the help of electric current, the process is called electrolysis.
\(\underset { Water }{ 2{ H }_{ 2 }O(I) } \overset { Electric\quad current }{ \longrightarrow } \underset { (Hydrogen\quad gas) }{ 2{ H }_{ 2 }(g) } +\underset { (Oxygen\quad gas) }{ { O }_{ 2 }(g) } \)

(a) Sodium (Na) > Aluminium (A1)> Copper (Cu) > Gold (Au).
(b) 3MnO₂(s) + 4A1(s) \(\overset { \Delta }{ \longrightarrow } \) 3Mn(l) + 2A1₂O₃(s)+ Heat.

(i) Increase in the strength of alkali. So the nature of solution will be basic.
(ii) Hydroxide ion or hydroxyl ion or OH^- ion.
(iii) A paper impregnated with the universal indicator is generally used to measure the pH of a solution.

The major differences between an electric motor and generator are stated below:
Electric Motor:
1. It converts electrical energy into mechanical energy.
2. It needs electrical energy for its works.
3. They are used as water pumps, marble grinders etc.
Generator:
1. It converts mechanical energy into electrical energy
2. It needs mechanical energy for its working.
3. They are used as water pumps, marble grinders etc.
4. diesel generator, hydro-electric generator are the examples of it.

The different constituents of blood are plasma (the fluid part of the bloo(d) and blood corpuscles consisting of RBCs, WBCs, and platelets)
WBCs are known as the soldiers of the body because they fight against the pathogenes that invade our body, thus preventing the occurence of diseases.

The transport of soluble products of photosynthesis is known as translocation. Translocation in plants occurs by means of the vascular tissue known as phloem. Translocation is necessary because without it, the food prepared by the leaves cannot reach other parts of the plant.
(i)In plants, the synthesis of sugars takes place in the leaves by the process of photosynthesis.
(ii)Hormones are synthesised away from their targrt site.

(a) Metal oxides-that react with both acids and bases to produce salt and water are known as amphoteric oxides. For example, zinc reacts with an acid or a base to produce salt and water.
\(ZnO+\underset { (Acid) }{ 2KCI } \rightarrow \underset { (Salt) }{ { ZnCI }_{ 2 } } +\underset { (Water) }{ { H }_{ 2 }O } \\ ZnO+\underset { (Base) }{ 2NaOH } \rightarrow \underset { (Salt) }{ { Na }_{ 2 }{ ZnO }_{ 2 } } +\underset { (Water) }{ { H }_{ 2 }O } \)
Amongst the given oxides, zinc oxide (ZnO) and aluminium oxide (AI₂O₃) are amphoteric oxides.
(b) Non - metals are electron acceptors. Hence, they cannot donate electrons to H⁺ ions to form hydrogen gas (H₂).

(a) The solar cells are costly and hence the energy available from them expensive.
(b) 15 km/h is the minimum wind velocity required to obtain useful energy with a windmill.
(c) Nuclear fission is the process in which a radioactive atom splits up into smaller nuclei when struck with low energy neutrons.

(a) A solar cell is a device which converts solar energy into electricity. It is a sandwich of a silicon-boron layer and a silicon-arsenic layer.
(b) Biogas is an ideal fuel for domestic use because it is a cheap and clean fuel, which does not leave behind any residue.
(c) A nuclear power plant is a device in which controlled chain reaction is used.

(i) Regions included in central nervous system are the brain and the spinal cord. The brain and the spinal cord. The brain is further divided into three parts - forebrain, midbrain, and hindbrain.
(ii) Three of the functions of the brain are:
Forebrain controls intelligence, learning, memory, thinking, speech, etc.
Midbrain is associated with the sense of sight and hearing.
Hindbrain controls all involuntary actions such as breathing, peristalsis, etc.

(ii) When the key is closed, total voltage applied across the circuit will be = 2 ✕ 5V = 10 V
     Total resistance (R) applied across the circuit in Ohms = 5+10+15= \(30\Omega \) 
     By Ohm's Law,
     Current (I) = \(\frac { V }{ R } \)
       \(I=\frac { 10 }{ 30 } =0.33A\)

A layer of basic copper carbonate is formed by the reaction of air on copper metal.
This layer being insoluble in water, cannot be cleaned with water alone. But, it is soluble in acids so lemon containing citric acid, tamarind containing tartaric acid or any other sour substance containing acid can be effective in cleaning the vessels. As these acids neutralises the basic copper carbonate and dissolves the layer. Hence, surface of copper vessels are cleaned with lemon or tamarind juice to give its characteristics lustre.

(i) A and B belong to group 1 and 2 because they form basic oxides. C belongs to group 13 as it has 3 valence electrons. D belongs to group 14 as it forms almost neutral oxide. E and F belong to group 15 and 16 as they form acidic oxides. G belongs to group 17 as it has 7 valence electrons and H belongs to group 18. They belong to 3rd period of Periodic Table because sodium belongs to 3rd period and AG is NaCl, ionic compound of sodium which can be obtained from sea water and A(Na) and G( Cl) belong to 3rd period.
(ii) H belong to noble gas.
(iii) A has the largest atomic radius.
(iv) E and F are likely to be non-metals.
(v) D is likely to be metalloid or semi-metal.

ii) Although wood is readily found in nature, it is still not a good source of energy because
- the energy obtained from per mass of Wood is very small.
- it produces a lot of smoke, which is very harmful for the environment and contributes to air pollution.
- using wood as a source of energy further increases the rate of deforestation.