A common flashlight bulb is rated at 0.30 A and 2.8 V (the values of the current
ID: 1547771 • Letter: A
Question
A common flashlight bulb is rated at 0.30 A and 2.8 V (the values of the current and voltage under operating conditions). If the resistance of the tungsten bulb filament at room temperature (20°C) is 1.7 , what is the temperature of the filament when the bulb is on?A common flashlight bulb is rated at 0.30 A and 2.8 V (the values of the current and voltage under operating conditions). If the resistance of the tungsten bulb filament at room temperature (20°C) is 1.7 , what is the temperature of the filament when the bulb is on?
A common flashlight bulb is rated at 0.30 A and 2.8 V (the values of the current and voltage under operating conditions). If the resistance of the tungsten bulb filament at room temperature (20°C) is 1.7 , what is the temperature of the filament when the bulb is on?
Explanation / Answer
from the ohm's law
V = IR
R= V/I
=2.8 V/0.30 A
=9.33 ohm
rletaion between reistance and temperature is
R = R0 + alpha*(T - T0)
9.33=1.7 +4.5 * 10^-3 T- (20+273) * 4.5 * 10^-3
T = 1988.55 K or 1988.55 K -273 = 1715.55 C