Derivation Of Ohms Law

A wire of resistance is stretched to twice its original length. The resistance of a stretched wire would be:
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Two metal wires of identical dimensions are connected in series. If are the conductivities of the metal wires respectively, the effective conductivity of the combination is:
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A circuit contains an ammeter, a battery of and a resistance $$ all connected in series. If the ammeter has a coil of resistance $$ and a shunt of $$ then the reading in the ammeter will be:
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Two solid conductors are made up of the same material and have the same length and the same resistance. One of them has a circular cross-section of area and the other one has a square cross-section of area The ratio of is:
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The resistance of platinum wire at is and at . The temperature coefficient of resistance of the wire is:
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