Answer
Verified
306.9k+ views
Hint: To answer this question students should know what is ohm’s law and equation of ohm’s law. Ohm’s law gives the relation between current passing and voltage applied across any circuit. Then what is resistance? How is it related to ohm’s law?
Complete step by step answer:
Ohm's law helps us in determining the values of resistance, the current flowing through a circuit, and the voltage applied. Hence with the help of these values, we can find the values of other factors like drift speed, resistivity and many more. It also allows us to calculate the value of power consumption.
$I\propto V$ or $I\propto V$
$ \Rightarrow V = IR$
Where R is a constant called resistance of the conductor. The value of this constant depends on the nature, length, area of cross section and temperature of the conductor.
As per Ohm's law we have,
$V = IR$
Were, $R = \rho \dfrac{l}{a} - - - - (1)$
Here, $\rho $ is the resistivity ‘l’ is the length of material and ‘a’ is the area of the material.
As the volume is constant,
Initial volume = final volume
$la = 2la' - - - - (2)$
(Here initially the length was l and it was increased by $100\% $ so the final length will become $2l$ )
$a' = \dfrac{a}{2}$
Now, substituting the value in the equation of resistance,
$ \Rightarrow R' = \rho \dfrac{{2l}}{{\dfrac{a}{2}}} - - - - (3)$
$ \Rightarrow R' = \rho \dfrac{{2l}}{a} \times 2 - - - - (4)$
Further simplifying we get
$ \Rightarrow R' = 4\rho \dfrac{l}{a}$
$ \Rightarrow R' = 4R$
Therefore, change in the resistance of stretched wire will be
$percentage{\text{ new }}R' = \dfrac{{final{\text{ resistance - initial resistance}}}}{{initial{\text{ resistance}}}} \times 100$
Substituting the given values
$ \Rightarrow {{\% }}R' = \dfrac{{4R - R}}{R} \times 100$
$ \Rightarrow \dfrac{{3R}}{R} \times 100 = 300\% $
$\therefore R' = 300\% $
Hence, the correct answer is option A.
Note: For ohm’s law it is a necessary condition that the temperature must be constant. It’s true only for linear electrical elements. For non-linear electrical elements with parameters like capacitance, resistance etc, the voltage and current won’t be constant with respect to time making it difficult to use Ohm’s law. Ohm’s law is not applicable for unilateral electrical elements like diodes and transistors as they allow the current to flow through in one direction only.
Complete step by step answer:
Ohm's law helps us in determining the values of resistance, the current flowing through a circuit, and the voltage applied. Hence with the help of these values, we can find the values of other factors like drift speed, resistivity and many more. It also allows us to calculate the value of power consumption.
$I\propto V$ or $I\propto V$
$ \Rightarrow V = IR$
Where R is a constant called resistance of the conductor. The value of this constant depends on the nature, length, area of cross section and temperature of the conductor.
As per Ohm's law we have,
$V = IR$
Were, $R = \rho \dfrac{l}{a} - - - - (1)$
Here, $\rho $ is the resistivity ‘l’ is the length of material and ‘a’ is the area of the material.
As the volume is constant,
Initial volume = final volume
$la = 2la' - - - - (2)$
(Here initially the length was l and it was increased by $100\% $ so the final length will become $2l$ )
$a' = \dfrac{a}{2}$
Now, substituting the value in the equation of resistance,
$ \Rightarrow R' = \rho \dfrac{{2l}}{{\dfrac{a}{2}}} - - - - (3)$
$ \Rightarrow R' = \rho \dfrac{{2l}}{a} \times 2 - - - - (4)$
Further simplifying we get
$ \Rightarrow R' = 4\rho \dfrac{l}{a}$
$ \Rightarrow R' = 4R$
Therefore, change in the resistance of stretched wire will be
$percentage{\text{ new }}R' = \dfrac{{final{\text{ resistance - initial resistance}}}}{{initial{\text{ resistance}}}} \times 100$
Substituting the given values
$ \Rightarrow {{\% }}R' = \dfrac{{4R - R}}{R} \times 100$
$ \Rightarrow \dfrac{{3R}}{R} \times 100 = 300\% $
$\therefore R' = 300\% $
Hence, the correct answer is option A.
Note: For ohm’s law it is a necessary condition that the temperature must be constant. It’s true only for linear electrical elements. For non-linear electrical elements with parameters like capacitance, resistance etc, the voltage and current won’t be constant with respect to time making it difficult to use Ohm’s law. Ohm’s law is not applicable for unilateral electrical elements like diodes and transistors as they allow the current to flow through in one direction only.
Recently Updated Pages
Basicity of sulphurous acid and sulphuric acid are
Assertion The resistivity of a semiconductor increases class 13 physics CBSE
Three beakers labelled as A B and C each containing 25 mL of water were taken A small amount of NaOH anhydrous CuSO4 and NaCl were added to the beakers A B and C respectively It was observed that there was an increase in the temperature of the solutions contained in beakers A and B whereas in case of beaker C the temperature of the solution falls Which one of the following statements isarecorrect i In beakers A and B exothermic process has occurred ii In beakers A and B endothermic process has occurred iii In beaker C exothermic process has occurred iv In beaker C endothermic process has occurred
The branch of science which deals with nature and natural class 10 physics CBSE
What is the stopping potential when the metal with class 12 physics JEE_Main
The momentum of a photon is 2 times 10 16gm cmsec Its class 12 physics JEE_Main
Trending doubts
Difference Between Plant Cell and Animal Cell
Difference between Prokaryotic cell and Eukaryotic class 11 biology CBSE
What is BLO What is the full form of BLO class 8 social science CBSE
Change the following sentences into negative and interrogative class 10 english CBSE
Fill the blanks with the suitable prepositions 1 The class 9 english CBSE
What organs are located on the left side of your body class 11 biology CBSE
The cell wall of prokaryotes are made up of a Cellulose class 9 biology CBSE
Select the word that is correctly spelled a Twelveth class 10 english CBSE
a Tabulate the differences in the characteristics of class 12 chemistry CBSE