Question

common flash light bulb is rated 3
ampere and 2.9 if the resistance of tungsten filament at 20 degree celsius is 1.1 ohm what is the temperature of the filament when the bulb is on​

Answer 1

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Answer 2

Given:

The common flash light bulb is rated 3  ampere and 2.9 if the resistance of tungsten filament at 20 degree celsius is 1.1 ohm.

To find:

What is the temperature of the filament when the bulb is on​?

Solution:

From given, we have,

Current = I = 3 A

Voltage = V = 2.9 V

R = V/I = 2.9/3 = 0.967 Ω

we use the formula,

R = R₀ [1 + α(T - T₀)]

we know, α = 4.5e-3

0.967 = 1.1 [1 + 4.5e-3(T - 20)]

0.8790 = 1 + 4.5e-3(T - 20)

T = 19.46 °C

The temperature of the filament when the bulb is on is 19.46 °C