A certain light-bulb has a tungsten filament. It has a power of 100 W when attached to 120 V potential difference.
a) Calculate the resistance of the filament.
b) If the length of the filament is 4 cm, what is its radius when cold.
c) How many electrons pass through it per second.
d) When the bulb is turned on, the temperature of the filament reaches 1200 C. Calculate the new resistance and power.
e) At 10 cents per kilowatt hour, what will be the cost of operating the light-bulb for 100 hours.