Consider the circuit below: The battery EMF equals 4.89 volt, the voltage across

Question

Consider the circuit below: The battery EMF equals 4.89 volt, the voltage across the light bulb equals 4.67 volt, and the current through the light bulb equals 166 mA. When the light bulb is removed from the circuit and its resistance is measured with an ohmmeter its resistance equals 3.00 Ohm (In other words. R_s = 3.00 Ohm) Calculate R_f, the resistance of the light bulb filament in this circuit. Calculate P_f. the power dissipated in the light bulb filament. Calculate T_f. the temperature of the light bulb filament. Calculate lambda_m, the wavelength corresponding to T_f.

Explanation / Answer

a) Resistance of light bulb = R = V/I = 4.67/0.166 = 28.1 ohm

b) Power dissipated = P = IV = 4.67*0.166 = 0.77522 W

c) Let 5 mm long, tightly wound filament with a mean diameter (after winding) of 0.5 mm, you would have a surface area of approximately 5 * * 0.5 ~ 8 mm2

I = P = 0.77522 W

Then T = (P/A)^0.25 = 1143.3 K

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