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QJEEM18Ph9290: JEE Main 2018 Physics - Class 12 JEEM18Ph9290 Solution: A copper rod of mass m slides under gravity on two smooth…

JEE Main 2018 (Online) 15th April Evening Slot Physics - Electromagnetic Induction Question 111 English
A copper rod of mass m slides under gravity on two smooth parallel rails, with separation l and set at an angle of θ with the horizontal. At the bottom rails are joined by a resistance R. There is a uniform magnetic field B normal to the plane of the rails, as shown in the igure. The terminal speed of the copper rod is :

Multiple Choice Options

  • A mgRtanθB2l2
  • B mgRcotθB2l2
  • C mgRsinθB2l2
  • D mgRcosθB2l2

Step-by-Step Verified Solution

JEE Main 2018 (Online) 15th April Evening Slot Physics - Electromagnetic Induction Question 111 English Explanation

At terminal velocity, net force on rod = mgsin⁡θ

⇒mgsin⁡θ=iBl

Now, IBl=(BvlR)Bl=B2l2vR

⇒mgsin⁡θ=B2l2vR⇒v=mgRsin⁡θB2l2

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