JEE Mains · Physics · STD 12 - 3. current electricity
A wire of resistance \(160\,\Omega\) is melted and drawn in wire of one-fourth of its length. The new resistance of the wire will be \(......\Omega\)
- A \(10\)
- B \(640\)
- C \(40\)
- D \(16\)
Answer & Solution
Correct Answer
(A) \(10\)
Step-by-step Solution
Detailed explanation
Volume \(=\) Constant \(A _1 L _1= A _2 L _2\) \(A _1 L = A _2 \frac{ L }{4}\) \(4 A _1= A _2\) \(R _1=\frac{\rho L_1}{ A _1} \quad R _2=\frac{\rho L_2}{ A _2}\) \(\frac{ R _2}{ R _1}=\frac{ L _2 A _1}{ A _2 L _1}=\frac{ L }{4} \frac{ A _1}{4 A _1 L }\)…
See the Complete Solution
Get step-by-step explanations for this and 2.5 Lakh+ more JEE, NEET & CET questions.
- Unlock all solutions
- Practice the full chapter
- Track accuracy across PYQs
4.8 rated on Google Play · 14,000+ reviews
More questions from Physics
- Considering a group of positive charges, which of the following statements is correct?JEE Mains 2023 Medium
- In the given figure, the face \(AC\) of the equilateral prism is immersed in a liquid of refractive index ' \(n\) '. For incident angle \(60^{\circ}\) at the side \(AC\), the refracted light beam just grazes along face \(AC\). The refractive index of the liquid \(n =\frac{\sqrt{ x }}{4}\). The value of \(x...\) is (Given refractive index of glass \(=1.5\) )
JEE Mains 2022 Medium - In figure, the optical fiber is \(I = 2\,m\) long and has a diameter of \(d = 20\,\mu \,m\). If a ray of light is incident on one end of the fiber at angle \({\theta _1} = {40^o}\) , the number of reflection it makes before emerging from the other end is close to
JEE Mains 2019 Hard - Moment of inertia about an axis \(AB\) for a rod of mass \(40\) kg and length \(3\) m is same as that of a solid sphere of mass of \(10\) kg and radius \(R\) about an axis parallel to \(AB\) axis with separation of \(3\) m as shown in figure below. The value of \(R\) is given as \(\sqrt{\dfrac{\alpha}{2}}\). The value of \(\alpha\) is _______.
JEE Mains 2026 Medium - Three force \(F_1=10\,N , F_2=8\,N , F _3=6\,N\) are acting on a particle of mass \(5\,kg\). The forces \(F _2\) and \(F _3\) are applied perpendicular so that particle remains at rest. If the force \(F_1\) is removed, then the acceleration of the particle is \(......ms^{-2}\)JEE Mains 2023 Medium
- Voltage rating of a parallel plate capacitor is \(500\,V\). Its dielectric can withstand a maximum electric field of \({10^6}\,\frac{V}{m}\). The plate area is \(10^{-4}\, m^2\) . What is the dielectric constant if the capacitance is \(15\, pF\) ? (given \({ \in _0} = 8.86 \times {10^{ - 12}}\,{C^2}\,/N{m^2}\))JEE Mains 2019 Hard
More PYQs from JEE Mains
- Given below are two statements Statement \(-I\) : A point charge is brought in an electric field. The value of electric field at a point near to the charge may increase if the charge is positive. Statement \(-II\) : An electric dipole is placed in a non-uniform electric field. The net electric force on the dipole will not be zero. Choose the correct answer from the options given belowJEE Mains 2022 Medium
- The ratio of the de-Broglie wavelengths of proton and electron having same kinetic energy: (Assume \(m_p=m_e \times 1849\) )JEE Mains 2023 Medium
- When the position vector \(\overrightarrow{ r }=x \hat{ i }+y \hat{ j }+z \hat{ k }\) changes sign as \(-\overrightarrow{ r }\), which one of the following vector will not flip under sign change ?JEE Mains 2026 Easy
- A vessel contains \(0.15\) m\(^3\) of a gas at pressure \(8\) bar and temperature \(140°\)C with \(c_p = 3R\) and \(c_v = 2R\). It is expanded adiabatically till pressure falls to \(1\) bar. The work done during this process is _______ kJ. (\(R\) is gas constant)JEE Mains 2026 Hard
- Consider the system of linear equation \(x+y+z=\) \(4 \mu, x+2 y+2 \lambda z=10 \mu, x+3 y+4 \lambda^2 z=\mu^2+15\), where \(\lambda, \mu \in R\). Which one of the following statements is \(NOT\) correct?JEE Mains 2024 Hard
- In an experiment with a convex lens. The plot of the image distance (\(v'\)) against the object distance \(\left(\mu^{\prime}\right)\) measured from the focus gives a curve \(v^{\prime} \mu^{\prime}=225\). If all the distances are measured in \(cm\). The magnitude of the focal length of the lens is \(cm\).JEE Mains 2022 Medium