JEE Main 2017 Question Paper (08-Apr-2017)

Question 1

According to Bohr's theory, the time-averaged magnetic field at the centre (i.e., nucleus) of a hydrogen atom due to the motion of electrons in the $n^{th}$ orbit is proportional to: ($n =$ principal quantum number)

Accepted Answer

${n}^{-5}$

Answer

${n}^{-3}$

Answer

${n}^{-2}$

Answer

${n}^{-4}$

Question 2

A magnetic dipole in a uniform magnetic field has: (Take zero potential energy when magnetic dipole is perpendicular to magnetic field)

Accepted Answer

Zero potential energy when the torque is maximum

Answer

Maximum potential energy occurs when the torque is maximum.

Answer

Zero potential energy when the torque is minimum

Answer

Minimum potential energy when the torque is maximum

Question 3

The $V-I$ characteristic of a diode is shown in the figure. The ratio of forward to reverse bias resistance is:

Accepted Answer

$10^{-6}$

Answer

$100$

Answer

${10}^{6}$

Answer

$10$

Question 4

A uniform disc of radius $ R $ and mass $ M $ is free to rotate only about its axis. A string is wrapped over its rim and a body of mass $ m $ is tied to the free end of the string as shown in the figure. The body is released from rest. Then the acceleration of the body is:

Accepted Answer

$\frac{2\, mg}{2m + M}$

Answer

$\frac{2\, Mg}{2m + M}$

Answer

$\frac{2\, \mathrm{M}g}{2M + m}$

Answer

$\frac{2\, mg}{2M + m}$

Question 5

An ideal gas has molecules with $5$ degrees of freedom. The ratio of specific heats at constant pressure $\left(C_{p}\right)$ and at constant volume $\left(C_{V}\right)$ is:

Accepted Answer

$\frac{7}{5}$

Answer

$6$

Answer

$ \frac{7}{2} $

Answer

$\frac{5}{2}$