-6 4. A copper wire has a diameter of 5.0 mm and cross-sectional area A = 2.0 x 10 m. It carries a current of 3.5 A. The resistivity of a copper is 1.72 x 10-8 Q2m. Find: (i) The magnitude of electric field in the wire. (3.01 x 10-2 V/m) (ii) The potential difference between two points in the wire. (0.75 V) (iii) The resistance of 25.0 m length of the wire. (0.215 (2) 5. An copper wire used in a house cable have a diameter of 1.5 mm. The resistivity and temperature coefficient of a material of copper are 1.72 x 10 m and 3.9 x 10 /C respectively. (i) What is the resistance of a 5.0 m long piece of aluminum wire? (0.152) (ii) If the wire has a resistance of 10.0 2 at 20.0C. What resistance will it have at 50.0C? (11.12) (iii) A current of 5.0 A flows in a resistor when a potential difference of 24.0 V is applied across it. What is the resistance of the wire? (4.82)