
The resistance of an incandescent lamp is
A. Greater when switched off
B. Smaller when switched off
C. Greater when switched on
D. The same whether it is switched off or switched on
Answer
161.1k+ views
Hint:When the electricity is passed through the resistance then it converts the electric energy to the heat energy and light energy as a result the temperature of the resistor increases.
Formula used:
\[\rho = {\rho _0}\left( {1 + \alpha \left( {\Delta T} \right)} \right)\]
Where, \[\rho \] is the final resistivity of material, \[{\rho _0}\] is the initial resistivity of material, \[\alpha \] is the temperature coefficient of the material’s resistivity and \[\Delta T\] is the change in temperature.
Complete step by step solution:
With increase in temperature the resistance increases as the resistivity of the material changes with variation of temperature as,
\[\rho = {\rho _0}\left( {1 + \alpha \left( {\Delta T} \right)} \right)\]
Here \[\rho \] is the final resistivity of material, \[{\rho _0}\] is the initial resistivity of material, \[\alpha \] is the temperature coefficient of the material’s resistivity and \[\Delta T\] is the change in temperature.
When the incandescent lamp is switched off then the electric circuit is not completed and hence there is no flow of electric current through the incandescent lamp. As there is no electric current through the incandescent lamp so there will be no generation of heat and light from the lamp. So the temperature of the incandescent lamp will remain the same as before. Hence, the resistance of the incandescent lamp will be the same.
When the incandescent lamp is switched on then the electric circuit is completed and hence there is flow of electric current through the incandescent lamp. As there is electric current through the incandescent lamp so there will be generation of heat and light from the lamp. So the temperature of the incandescent lamp will increase. Hence, the resistance of the incandescent lamp increases. So, the resistance of the incandescent lamp will be greater when switched on.
Therefore, the correct option is C.
Note: The resistivity of the material of the resistor is directly proportional to the change in temperature and also the resistance is directly proportional to the resistivity of the material. Hence, with increase in temperature the resistance increases.
Formula used:
\[\rho = {\rho _0}\left( {1 + \alpha \left( {\Delta T} \right)} \right)\]
Where, \[\rho \] is the final resistivity of material, \[{\rho _0}\] is the initial resistivity of material, \[\alpha \] is the temperature coefficient of the material’s resistivity and \[\Delta T\] is the change in temperature.
Complete step by step solution:
With increase in temperature the resistance increases as the resistivity of the material changes with variation of temperature as,
\[\rho = {\rho _0}\left( {1 + \alpha \left( {\Delta T} \right)} \right)\]
Here \[\rho \] is the final resistivity of material, \[{\rho _0}\] is the initial resistivity of material, \[\alpha \] is the temperature coefficient of the material’s resistivity and \[\Delta T\] is the change in temperature.
When the incandescent lamp is switched off then the electric circuit is not completed and hence there is no flow of electric current through the incandescent lamp. As there is no electric current through the incandescent lamp so there will be no generation of heat and light from the lamp. So the temperature of the incandescent lamp will remain the same as before. Hence, the resistance of the incandescent lamp will be the same.
When the incandescent lamp is switched on then the electric circuit is completed and hence there is flow of electric current through the incandescent lamp. As there is electric current through the incandescent lamp so there will be generation of heat and light from the lamp. So the temperature of the incandescent lamp will increase. Hence, the resistance of the incandescent lamp increases. So, the resistance of the incandescent lamp will be greater when switched on.
Therefore, the correct option is C.
Note: The resistivity of the material of the resistor is directly proportional to the change in temperature and also the resistance is directly proportional to the resistivity of the material. Hence, with increase in temperature the resistance increases.
Recently Updated Pages
JEE Main 2021 July 25 Shift 1 Question Paper with Answer Key

JEE Main 2021 July 22 Shift 2 Question Paper with Answer Key

JEE Atomic Structure and Chemical Bonding important Concepts and Tips

JEE Amino Acids and Peptides Important Concepts and Tips for Exam Preparation

Chemical Properties of Hydrogen - Important Concepts for JEE Exam Preparation

JEE General Topics in Chemistry Important Concepts and Tips

Trending doubts
JEE Main 2025 Session 2: Application Form (Out), Exam Dates (Released), Eligibility, & More

JEE Main 2025: Derivation of Equation of Trajectory in Physics

Electric Field Due to Uniformly Charged Ring for JEE Main 2025 - Formula and Derivation

Electric field due to uniformly charged sphere class 12 physics JEE_Main

Displacement-Time Graph and Velocity-Time Graph for JEE

Uniform Acceleration

Other Pages
JEE Advanced Marks vs Ranks 2025: Understanding Category-wise Qualifying Marks and Previous Year Cut-offs

JEE Advanced 2025: Dates, Registration, Syllabus, Eligibility Criteria and More

JEE Advanced Weightage 2025 Chapter-Wise for Physics, Maths and Chemistry

Degree of Dissociation and Its Formula With Solved Example for JEE

Free Radical Substitution Mechanism of Alkanes for JEE Main 2025

If a wire of resistance R is stretched to double of class 12 physics JEE_Main
