In her bathroom, Mindy has an overhead heater that consists of a coiled wire made of nichrome that gets hot when turned on. The wire has a length of 3.4 m when it is uncoiled. The heating element is attached to the normal 120-V wiring and when the wire is glowing red hot it has a temperature of about 428° C and dissipates 2220 W of power. Nichrome has a resistivity of 1.08 10-6 m at 20° C and a temperature coefficient of resistivity of 0.00040° C ?1.
(a) What is the resistance of the heater when it is turned on? ?
(b) What current does the wire carry? A
(c) If the wire has a circular cross section, what is its diameter? Ignore the small changes in the wire's diameter and length due to changes in temperature. m
(d) When the heater is first turned on, it has not yet heated up, so it is operating at 20° C. What is the current through the wire when it is first turned on?