KVPY Stream SB-SX (Class 12 & 1st Year B.Sc.) Physics: Questions 60 - 62 of 268

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Question number: 60

» Work, Energy and Power » Work-Energy Theorem

Appeared in Year: 2012

MCQ▾

Question

In one model of the election, the mass of electron me is thought to be a uniformly charged shell of radius R and total charge e, whose electrostatic energy E is equivalent to its mass me via Einstein’s mass energy relation E = mec2. In this model, R is approximately – (me = 9.1 × 10-31kg, c = 3 × 108 ms-1, 14πϵ0=9×109Faradsm1, magnitude of the electron charge = 1.6 × 10-19 C)

Choices

Choice (4) Response

a.

1.4×1015m

b.

2.8×1035m

c.

2×1013m

d.

5.3×1011m

Question number: 61

» Laws of Motion » Law of Conservation of Linear Momentum

Appeared in Year: 2011

MCQ▾

Question

At a distance l from a uniformly charged long wire, a charged particle is thrown radially outward with a velocity u in the direction perpendicular to the wire. When the particle reaches a distance 2l from the wire its speed is found to be 2u . The magnitude of the velocity, when it is a distance 4l away from the wire, is (ignore gravity)

Choices

Choice (4) Response

a.

2u

b.

3u

c.

22u

d.

4u

Question number: 62

» Work, Energy and Power » Work Done

Appeared in Year: 2012

MCQ▾

Question

A conducting rod of mass m and length l is free to move without friction on two parallel long conducting rails, as shown below. There is a resistance R across the rails. In the entire space around, there is a uniform magnetic field B normal to the plane of the rod and rails. The rod is given an impulsive velocity v0.

A conducting rod move on two parallel long conducting rails

A Conducting Rod Move on Two Parallel Long Conducting Rails

In figure a conducting rod of mass m and length l is free to move without friction on two parallel long conducting rails.

Finally, the initial energy 12mv02

Choices

Choice (4) Response

a.

will be converted fully into magnetic energy due to induced current

b.

will enable rod to continue to move with velocity v0 since the rails are frictionless

c.

will be converted fully into heat energy in the resistor

d.

will be converted into the work done against the magnetic field

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