JEE Main 2020 Question Paper (09-Jan-2020) (Shift 1)

Question 1

Radiation, with wavelength $6561 \mathrm{\AA}$, falls on a metal surface to produce photoelectrons. The electrons are made to enter a uniform magnetic field of $3 	imes 10^{-4} \mathrm{T}$. If the radius of the largest circular path followed by the electrons is $10 \mathrm{mm}$, the work function of the metal is close to:

Accepted Answer

$1.1\mathrm{eV}$

Answer

$1.6 \mathrm{eV}$

Answer

$0.8\,\mathrm{eV}$

Answer

$1.8\,\mathrm{eV}$

Question 2

A quantity $ f $ is given by $ f = \sqrt{\frac{h c^{5}}{G}} $ where $ c $ is the speed of light, $ G $ is the universal gravitational constant, and $ h $ is Planck’s constant. The dimension of $ f $ is that of:

Accepted Answer

energy

Answer

area

Answer

momentum

Answer

volume

Question 3

Consider a force $ \overrightarrow{F} = -x \widehat{i} + y \widehat{j} $. The work done by this force in moving a particle from point $ A(1,0) $ to $ B(0,1) $ along the line segment is: (all quantities are in SI units)

Accepted Answer

$1$

Answer

$2$

Answer

$ \frac{1}{2} $

Answer

$ \frac{3}{2} $

Question 4

Water flows in a horizontal tube (see figure). The pressure of water changes by $700 N\,m^{-2}$ between points $A$ and $B$, where the areas of cross section are $40 cm^{2}$ and $20 cm^{2}$, respectively. Find the rate of flow of water through the tube. (Density of water $= 1000 kg\,m^{-3}$.)

Accepted Answer

$2720\,\mathrm{cm}^3/\mathrm{s}$

Answer

$3020\,\mathrm{cm}^3/\mathrm{s}$

Answer

$2420\,\mathrm{cm}^3/\mathrm{s}$

Answer

$1810\,\mathrm{cm}^{3}/\mathrm{s}$

Question 5

A long, straight wire of radius $ a $ carries a current distributed uniformly over its cross-section. The ratio of the magnetic fields due to the wire at distances $ \frac{a}{3} $ and $ 2a $, respectively, from the axis of the wire is:

Accepted Answer

$\frac{2}{3}$

Answer

$2$

Answer

$ \frac{1}{2} $

Answer

$ \frac{3}{2} $