Q. 13.5( 2 Votes )

If a constant potential difference is applied across a bulb, the current slightly decreases as time passes and then becomes constant. Explain.

Answer :


We know Joule’s heating effect –


Joule’s heating effect is the process by which the passage of an electric current through a conductor produces heat


When a constant potential difference is applied across a bulb, due to Joule’s heating effect, the temperature of the bulb increases.


We know in case of metals, the temperature co-efficient is positive, which means, with increase in temperature, the Resistance of the metal increases.


In case of metals, the resistance and temperature is related as -



Where,


R= resistance at some temperature T


R0 = resistance at zero temperature


and = Temperature co-efficient.


From ohm’s law


Voltage,


Where


I is the current


R is the resistance


Thus, from the above formula, we get that with increase in resistance, current decreases. if the voltage remains constant


Now, the heat generated by the resistance is constantly radiated through the connecting wires into the surroundings.


Thus, the value of its temperature is maintained constant and so its resistance.


As a result, the current through the bulb filament becomes constant.


Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos
Check your knowledge of Electric Potential | QuizCheck your knowledge of Electric Potential | QuizCheck your knowledge of Electric Potential | Quiz45 mins
Electric Charges and Fields - 05Electric Charges and Fields - 05Electric Charges and Fields - 0556 mins
Electric Charges and Fields - 08Electric Charges and Fields - 08Electric Charges and Fields - 0854 mins
Electric Charges and Fields - 02Electric Charges and Fields - 02Electric Charges and Fields - 0256 mins
Electric Charges and Fields - 10Electric Charges and Fields - 10Electric Charges and Fields - 1055 mins
Electric Charges and Fields - 03Electric Charges and Fields - 03Electric Charges and Fields - 0352 mins
Electric Charges and Fields - 01Electric Charges and Fields - 01Electric Charges and Fields - 0155 mins
Electric Charges and Fields - 09Electric Charges and Fields - 09Electric Charges and Fields - 0946 mins
Equation of electric and magnetic fieldEquation of electric and magnetic fieldEquation of electric and magnetic field52 mins
Drift Velocity & Thermal VelocityDrift Velocity & Thermal VelocityDrift Velocity & Thermal Velocity34 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
caricature
view all courses
RELATED QUESTIONS :