Temperature Effect on Resistance
Resistance of most materials decreases with decreasing temperature. To demonstrate this effect a light bulb is connected in series with a coil of very fine copper wire and a DC power supply. The voltage is adjusted so that the bulb glows dimly. When the coil is immersed in liquid nitrogen the very fine copper wire will cool and the resistance of the wire decreases causing the current to increase and the bulb to glow brightly.