Question

(b) (i) A piece of nichrome wire (a Ni-Cr alloy) has a resistance of 6.5 12. The wire has a length of 10 cm and a diameter of 1.2 mm. Calculate the electrical resistivity and conductivity of this wire. (3) You now connect a voltage source to your Ni-Cr wire, using it as a resistive element. (ii) What would happen to the temperature of the wire ? (1) (iii) What would happen to the resistance as the temperature changes ? (1) (iv) Why do we see this trend in resistance with temperature in this material ? (1)

Answer 1

ou ci given length I= 10 cm = 0.1m diameter da - 2mm So Area A= T d2 (12)X10S = 2 4 M Resistance R = 6.52 we have formula R = se А 6.5 = á IT X (1.2)exios 4 3 = 6.5 MT ( 7 2)X10-6 0.) 4 - 5 se 7.351 X10 nim Resistivity a Conductivity 11 s 7.351 X10-5 o = 13602.98.5lm An

رزن) Connected to Voltage If it is a resistance element. using The temperature dissipated in wire due to of Nichrome wire , because of heat it's 6*5 n. Energy I2RE here R- Resistance of wire t> time I aument so This heat (Energy will increase the temp.) ر11 ) we know - Rg R. (1+* A7) Where a temperature Constant for material, AT a change in temperature. If 07f, Resis lence (Rg) A So (iv) We see this trend in resistance with temperature in this material because it has temperature Coefficient that is positive. it will change So