In a domestic circuit, parallel connection of devices is preferable for several reasons:
a. In series connection, if one of the devices is defective, if one of the devices is defective,     then the current of the entire circuit is cut off. As a result, all the devices stop working. In parallel connection, even if one device is defective, the others continue working.
b. In series connection, selective operation of devices is not possible, but this is not so in the case of parallel connection.
c. In series connection, the same current passes through all the devices, regardless of the fact that different devices require different values of current to operate. In parallel connection, different values of current can be obtained for different devices according to their requirements.

Cerebellum.

The receptors present in our eyes are called photoreceptors, as they are light sensitive.

It behaves like a magnet.

The main difference lies in the difference in the sex chromosome of sperm (male gamete) and egg (female gamete). The main difference between sperms and eggs of humans is that half of the sperms of a male (father) will have X chromosomes and the other half will have Y chromosomes. All the eggs of female (mother) will have only X chromosomes.
Importance.
(a) If the father contributes X chromosome, then the baby born will be a girl.
(b) If the father contributes Y chromosome, then the baby born will be a boy. Thus, the sperm determines the sex of a child.

Green plants are called 'producers' because they can produce food by photosynthesis in the presence of sunlight.

(i) Hexane: C₆H₁₄
(ii) Benzene: C₆H₆

(i)The glottis is gaurded by epiglottis because it prevents the entry of food in wind pipe. If the food enters wind pipe, then it chokes it, leading to the death of the person.
(ii)The lung alveoli are covered with blood vessels because the oxygen that we inhale dissolves in the blood, present in these blood capillaries only, as it reaches the lungs.
(iii)The wall of trachea is supported by cartilage rings because these rings prevent the air passage from collapsing.

Breathing is the process by which oxygen is taken in (inhalation) and carbon dioxide is released out (exhalation). Respiration involves the oxidation of the food we eat to release energy. Carbon dioxide produced as a result of this is released out during exhalation.
Aerobic respiration: During aerobic respiration, the oxidation of food takes place in the presence of oxygen. Aerobic respiration can be summarised by the given equation:
\({ C }_{ 6 }{ H }_{ 12 }{ O }_{ 6 }+{ 6O }_{ 2 }\longrightarrow { 6CO }_{ 2 }+{ 6H }_{ 2 }O+Energy\)
Anaerobic respiration: During anaerobic respiration, food is broken down in the absence of oxygen. It is also known as fermentation and is more common in microorganisms such as yeast.
Sometimes pyruvate gets converted into lactic acid in muscles by the process of anaerobic respiration.
\({ C }_{ 6 }{ H }_{ 12 }{ O }_{ 6 }\xrightarrow [ ]{ Absenceofoxygen } Alcohol+{ CO }_{ 2 }+{ H }_{ 2 }O+Energy\)

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.

If magnification is 1, the image size is same as that of object size.
Since, magnification is positive, the image is erect and virtual.

(i) Salt that contains water of crystallisation.
(ii)Washing soda - Na₂CO₃.10H₂O
Gypsum - CaSO₄.2H₂O
Plaster of pans - CaSO₄.\(1\over 2\)H₂O

(i) Copper is more reactive than silver. Hence, when copper wire is dipped in silver nitrate solution, it displaces silver from AgNO₃ solution forming copper nitrate which is bluish green in colour.
\((ii)\quad Cu+2AgN{ O }_{ 3 }\longrightarrow \underset { Copperr\quad (II)\quad nitrate\\ bluish\quad green }{ Cu{ (N{ O }_{ 3 }) }_{ 2 } } +\underset { Silver }{ 2Ag } \)

When baking soda is heated, it decomposes to produce sodium carbonate, water and CO₂ gas.
\(2NaHCO_3 \xrightarrow{\Delta} Na_2CO_3 + H_2O+ CO_2\)
CO₂ gas produced during the reaction makes the cake or bread spongy and fluffy.

(i)Anchoring the plant
(ii)Source of water and minerals
(iii)Availability of oxygen for respiration of root cells
(iv)Symbiotic association with microbes.

The mechanism of urine formation includes three steps namely,
(i) Glomerular ultra-filtration
(ii) Tubular reabsorption
(iii) Tubular secretion
(i)Glomerular Ultrafiltration:
Ultrafiltration of blood takes place inthe Malphighian body which acts as a biological filter. A Malphighian body comprises of Bowman's capsule and glomeruli.
The blood from the kidney flows through the capillaries of glomerulus where the blood pressure, is comparatively high and so brings about effective filtration. The hydrostatic pressure of the blood is always greater than the opposing pressures existing in the plasma protein and renal capillaries. Thus, the available net filtering force is chiefly responsible for glomerular filtration. The fluid in the capsule which is obtained by this process is termed glomerular filtrate. In man it is about 125ml/min. In 24 hours, the total volume of glomerular filtrate is 170 to 180 litres.
(ii) Tubular Reabsorption: Reabsorption takes place in the 'uriniferous tubules. Reabsorption of useful substances is a differential or selective process. The glomerular filtrate contains many useful substances such as glucose, amino acids, mineral salts and vitamins dissolved in large amount of water. Substances such as glucose, sodium and calcium, are actively reabsorbed in large quantities. Substances like urea and uric acid etc are reabsorbed in small quantities by a simple diffusion process or passive reabsorption. Substances like creatinine are not reabsorbed. They are completely eliminated.
Proximal convoluted tubule is responsible for the reabsorption of water, glucose, sodium phosphate and bicarbonates. On entering the distal convoluted tubule, the urine becomes nearly isotonic to the surrounding tissue fluid due to the active transport of sodium and passive transport of water. As urine (isotonic) passes into the collecting tubule it becomes once again hypertonic by the osmotic reabsorption of water under the influence of the hormone ADH. Thus the urine formed contains 96% of water, 2% urea and 2% of the metabolic products.
(iii) Tubular Secretion: This is the final step in the formation of urine during which the walls of tubule actively remove additional waste substances which are harmful to the body from the blood that have escaped filtration.

(i) An alloy is a homogenous mixture of two or more metals. It sometimes contains a non -metal component also.
(ii) It is made by heating the components in a definite proportion and then uniformly mixing them in the molten state and then cooling.
(iii) Two purposes of making alloys are:
     (a) To make a substance resistant to corrosion
     (b) To make a substance strong and hard
(iv) Constituents of Stainless steel:
     Iron, nickel, and chromium
(v) Two properties of stainless steel are:
     (a) It is resistant to corrosion.
     (b) It is more durable.
(vi) Constituents of Brass:
      Copper and Zinc
(vii) Two properties of brass are:
       (a) It is resistant to corrosion.
      (b) It is more malleable.

Gamete is formed as a result of meiosis in gametogenic cells. Zygote is formed after fusion of two different kinds of gametes. Different types of gametes are formed by different parents. Zygote is formed in the female reproductive part only.
Role of gamete in sexual reproduction: Gamete formation results in halving of number of chromosomes which is necessary to maintain the number of chromosomes in an organism which reproduces sexually.
Role of zygote in sexual reproduction: Zygote formation makes the number of chromosome equal to the somatic cells. further, it is the zygote which undergoes mitosis to develop into an embryo and subsequently into a new individual.

Detergents chemically are sodium or potassium salts of sulphonic acid of benzene or alkene.
Merits:
(i) They work well with hard water.
(ii) They are more effective than soaps.
Demerits:
(i) They are expensive.
(ii) Some of them having branching are non-biodegradable, therefore create water pollution.
Detergents are suitable for hard water having Mg²⁺ and Ca²⁺ ions because they do not form insoluble salts with Mg²⁺ and Ca²⁺ ions.

(a) Laws of Refraction: 
(i) The first law of refraction of light states that the incident ray, the refracted ray and the normal at the point of incidence, all lie in the same plane. 
(ii) The second law of refraction of light is the Snell's Law of Refraction. It state that the ratio of sine of the angle of incidence to the sine of angle of refraction is a constant for a given pair of medium.
\(\frac { sin\quad i }{ sin\quad r } =Constant(n)\)
This constant (n) is called refractive index of the medium. 
(i) When the light is going from vacuum to another medium, then the value of refractive index is called the absolute refractive index. 
(ii) The ratio of speed of light in vacuum to the speed of light in a medium is called the absolute refractive index of that medium, 
i.e. 
Absolute refractive index (of a medium)
\(=\frac { Speed\quad of\quad light\quad in\quad vacuum(c) }{ Speed\quad of\quad light\quad in\quad medium(v) } \)
(b) \(_{ a }{ { n }_{ w } }=\frac { 4 }{ 3 } ,_{ a }{ { n }_{ g } }=\frac { 3 }{ 2 } \)
Speed of light in glass, v_g= 2 x 10⁸ m/s 
Speed of light in air, v_g= ? 
Speed of light in water, v_w =?
\(_{ a }{ { n }_{ w } }=\frac { { v }_{ a } }{ { v }_{ w } } \)
\(\Rightarrow \frac { 4 }{ 3 } =\frac { { v }_{ a } }{ { v }_{ w } } \)      ...(i)
\(_{ a }{ { n }_{ g } }=\frac { { v }_{ a } }{ { v }_{ g } } \)
\(\Rightarrow \frac { 3 }{ 2 } =\frac { { v }_{ a } }{ 2\times { 10 }^{ 8 } } \)

Putting the value of v_a in equation (i),
\(\frac { 4 }{ 2 } =\frac { 3\times { 10 }^{ 8 } }{ { v }_{ w } } \)
\(\Rightarrow { v }_{ w }=3\times { 10 }^{ 8 }\times \frac { 3 }{ 4 } =\frac { 9 }{ 4 } \times { 10 }^{ 8 }\)
=2.25x10⁸ m/s.