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Q 1. Name the major constituent of biogas. List three characteristics to prove it as an excellent fuel. Solution Methane Smokeless, leaves no residue, higher heat of combustion. Q 2. (a) What is solar cell panel? (b) Name any two elements that are used for making solar cell panels. Solution (a) Solar Cell Panel: A combined arrangement of a large number of solar cells that can deliver sufficient electricity for practical use. (b) Silicon, germanium Q 3. How were fossil fuels formed? Solution The dead plants and animals which were buried deep under the earth for millions of years got converted into fossil fuels like coal, petroleum and natural gas. This happens because of absence of oxygen, high pressure, heat and bacterial action. Q 4. State two limitations of solar energy. Solution  1) The solar energy reaches the earth's surface in a diffused form. It has been estimated that the solar energy received in the upper atmosphere is 1.4 kW/m 2 . Thus, it...
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Q 1. A current through a horizontal power line flows in east to west direction. What is the direction of magnetic field at a point directly below it and at a point directly above it? Solution The electric current is flowing horizontally in east to west direction. Applying right hand thumb rule, we find that   i. The direction of magnetic field at a point directly below the wire is from north to south. ii. The direction of magnetic field at a point directly above the wire is from south to north. Q 2. What is a generator? Name the principle used in generator. Solution Generator is a device that converts mechanical energy to electrical energy. It works on the principle of electromagnetic induction. Q 3. When is the force on a current carrying wire maximum or minimum? Solution The force on a current carrying wire is maximum only when the wire is perpendicular to the direction of magnetic field. It is minimum, that is, no force acts on the conductor when it is p...
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Q 1. A particular resistance wire has a resistance of 3 ohm per meter. Find : (a) The total resistance of three lengths of this wire each 1.5 m long, in parallel. (b) The potential difference of the battery which gives a current of 2 A in each of the 1.5 m length when connected in the parallel to the battery (assume that resistance of the battery is negligible). (c) The resistance of 5 m length of a wire of the same material, but with twice the area of cross section. Solution Resistance of 1m of wire = 3 ohmResistance of 1.5 m of wire = 3 x 1.5 = 4.5 W      I = 2 AV = IR = 2 x 4.5 = 9 V R = 3 ohm for 1 mFor 5 m : R=3 x 5 = 15 ohmBut Area A is double i.e. 2A and resistance is inversely proportional to area so the resistance will be half.→ R = 15 / 2 = 7.5 ohm Q 2. Name the physical quantity whose unit is volt/ampere. Solution Resistance or electrical resistance.   Q 3. What is meant by the statement that th...
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