**Aluminum wire has a radius of 0.25 mm. and length of 75mm. If the resistance of the wire is 10 ohm. Calculate the resistivity of aluminum.****A wire of length of l and area of cross-section A was drawn into a wire of double the length by melting it. If its original resistivity and resistance were p and R respectively. What will be its new resistivity and resistance?****A wire of length of l and area of cross section A was drawn into a wire of double the length by melting it. If its resistance was 20 Ohm. What will be its new resistance?****A wire of resistance 10 ohms is drawn out so that its length is thrice the original length. Find its new resistance (resistivity and density of the wire does not change.)****A wire of resistance 16 ohm is drawn out so that its length is half the original length. Find the percentage change in resistance (resistivity and density of the wire does not change.)**

**What length of a copper wire of cross of copper -sectional = area0.01 square would be required to obtain a resistance of 1kohm. Resistivity copper =1.7×10-8 ohm m.****The specific resistance of a metal wire is 64×10 −6 Ωcm., the length is 198 cm and the resistance is 7Ω. The radius of the wire is?****A negligibly small current is passed through a wire of length 15 m and uniform cross-section 6.0×10−7 m**^{2}, and its resistance is measured to be 5.0 Ω. What is the resistivity of the material at the temperature of the experiment?**A copper wire has a diameter of 0.5 mm and a resistivity of 1.6 × 10–8 ohm m.**

**(a) What will be the length of this wire to make its resistance 10 ohm?**

**(b) How much does the resistance change if the diameter is doubled ?****Give one example to show how the resistance depends on the nature of material of the conductor.**

**(b) Calculate the resistance of an aluminium cable of length 10 km and diameter 2.0 mm if the resistivity of aluminum is 2.7 × 10–8 Ohm m.****Calculate the area of cross-section of a wire if its length is 1.0 m, its resistance is 23 ohm and the resistivity of the material of the wire is 1.84 × 10**^{–6}ohm m.**. The electrical resistivities of four materials A, B, C and D are given below :**

**A 110 × 10–8 Ohm-m**

**B 1.0 × 10**^{10}Ohm-m

**C. 10.0 × 10**^{–8}Ohm-m

**D.2.3 × 10**^{3}Ohm-m

**Which material is : (a) good conductor (b) resistor (c) insulator, and (d) semiconductor?**

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