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The situation in which live and neutral wire come in direct contact, abruptly increasing the current in the circuit is called short- circuiting.

Factor- Insulation of wire is damaged/fault in the appliance.

Safety device- an electric fuse. An electric fuse is an application of Joule's heating, If there is a current larger than the specified, value to, break the electric circuit and stop the flow of unduly high electric current.

Direct current does not change its direction with time whereas alternating current reverses its direction periodically.

Most power stations produce AC in India/an AC generator.

Electric power can be transmitted over Long distances without much loss of energy.

Electrical appliance - fan, washing machine, mixer.

Fleming's Left-Hand Rule - It states that "Stretch the forefinger, the central finger and the thumb of your left hand are mutually perpendicular to each other. If the forefinger shows the direction of the magnetic field and the central finger that of the current then the thumb will point towards the direction of motion of the conductor.

(i) Live wire 

(ii) Neutral wire 

(iii) Earth wire : 

Earth wire, colour of insulation - green 

The metallic body connected to the earth wire keeps its potential to that of the earth's zero potential and if there are any.leakage the user does not get any kind of electric shock.

(iii) (C) and (D)

• This is the idea before Rutherford’s model. 
• According to Rutherford’s model, number of protons inside the nucleus and number of electrons outside the nucleus are equal. 
• Hence the net negative charge is equal to net positive charge. So, the atom is electrically neutral.

(i) Cl^– ion form fcc lattice and Na⁺ ions occupy all octahedral voids of the unit cell. 

The coordination number in a square close packed structure in two dimensions is 4.

(i) Cl^– ion form fcc lattice and Na⁺ ions occupy all octahedral voids of the unit cell.

(iv) The fraction of octahedral or tetrahedral voids occupied depends upon the radii of the ions occupying the voids.

The property of carbon atom to form bonds with itself resulting in a single large structure or chain is called catenation.

Water Gas is also called as syngas or synthesis gas as it is used to synthesize methanol and simple hydrocarbons. It is used as an industrial fuel also.

(ii) The total number of tetrahedral voids in the face centred unit cell is 8.

1. c 

2. a 

3. d 

4. b

(ii) Ferromagnetic substances cannot be magnetised permanently.

1. It produces lot of heat as it is easily burnt. 

2. It does not leave any residue. 

3. It bums without smoke and so causes no pollution. 

4. This can be easily supplied through pipes. 

5. It can be directly used as fuel in homes and industries.

(ii) Ferromagnetic substances cannot be magnetised permanently.

CNG – Compressed Natural Gas. 

1. It is the cheapest and cleanest fuel. 

2. Vehicles using this gas produce less carbon dioxide and hydrocarbon emission. 

3. It is less expensive than petrol and diesel.

1. fertilizers 

2. trees, plants 

3. water 

4. hydrogen sulphide 

5. Propane 

6. Butane

7. Conventional 

8. Sub-bituminous 

9. Activated charcoal 

10. kidney dialysis

(a)  methane

(ii) equal number of cations and anions are missing from the lattice.

1. Most of the hydrocarbons are insoluble in water. 

2. Hydrocarbons are less dense than water. So they float on top of water. 

3. Most hydrocarbons react with oxygen to produce carbon dioxide and water.

(iv) To get a  n-type semiconductor from silicon, it should be doped with a substance with valence 5.

(ii) n-type semiconductor

(i) Frenkel defect

If the coal beds lie within 22 feet of the Earth’s surface, the top soil is removed and coal is dug out. This is called surface mining.

1. Natural gas is used as an industrial and domestic fuel. 

2. It is used in thermal power stations. 

3. It is used as fuel in vehicles as an alternative for petrol and diesel.

(iii) Assertion is correct statement but reason is wrong statement.

(ii) equal number of cations and anions are missing from the lattice.

To get a n-type semiconductor from silicon, it should be doped with a substance with valence 5

1. Bio-gas is a mixture of methane and carbon dioxide. 

2. It is produced by the decomposition of plant and animal waste which form the organic matter.

3. The breaking down of organic matter in anaerobic condition (ie., in the absence of oxygen) leads to the formation of biogas. 

4. It is an example for renewable source of energy

(ii) neutral

On doping germanium with galium some of the positions of lattice of germanium are occupied by galium. Galium atom has only three valence electrons. Therefore, fourth valency of nearby germanium atom is not satisfied. The place remains vacant. This place is deficient of electrons and is therefore called electron hole or electron vacancy. Electron from neighbouring atom comes and fills the gap, thereby creating a hole in its original position. Under the influence of electric field electrons move towards positively charged plates through these holes and conduct electricity. The holes appear to move towards negatively charged plates.

1. Coke contains 98% carbon. It is porous, black and the purest form of coal. 

2. It is a good fuel and burns without smoke. 

3. It is largely used as a reducing agent in the extraction of metals from their ores. 

4. It is also used in making fuel gases like producer gas and water gas which is a mixture of carbon monoxide and hydrogen.

(c) CH₃COONa

(a) Tomato – tartaric acid

(d) Natural gas

Correct answer is (b) HCl

(a) Due to annealing over a number of years glass acquires some crystalline character 

(b) because it loose oxygen

ZnO →Zn²⁺ + 1/2O₂ + 2e

Metal excess defect electron in interstitial voids the colour is yellow as the remaining colour of white light are absorbed by these electron.

1. Third law of thermodynamics

2. Entropy of a perfectly crystalline substance is zero at absolute zero temperature.

Packing efficiency is the % of total space filled by the particle.

OR,

Packing efficiency = 

\(\frac{\text{volume occupied by spheres in the unit cell}}{\text{total volume of the unit cell}}\times100\) 

Crystalline solids: Naphthalene, benzoic acid, potassium nitrate, copper.

Amorphous solids: Polyurethane, teflon, polyvinyl chloride, fibre glass, cellophane.

Every Sr²⁺ ion causes one cation vacancy (because two Na⁺ ions are replaced by one Sr²⁺ and it occupies the site of one Na⁺ ion and the other site remains vacant.)

Therefore, introduction of 10^-3 moles of SrCl₂ per 100 moles of NaCl would introduce 10^-3 moles cation vacancies in 100 moles of NaCl. No. of vacancies per mole of NaCl = \(\frac{10^{-3}}{100}\times6.02\times10^{23}\)

= 6.02 × 10¹⁸