JEE Main 2018 Question Paper (15-Apr-2018) (Shift 2)

Question 1

A solid ball of radius R has a charge density $\rho$ given by $\rho=\rho_0(1-\frac{r}{R})$ for $0< r< R$. The electric field outside the ball is :

Accepted Answer

$\frac{\rho_0R^3}{12\in_0 r^2}$

Answer

$\frac{4\rho_0R^3}{3\in_0 r^2}$

Answer

$\frac{3\rho_0R^3}{4\in_0 r^2}$

Answer

$\frac{\rho_0R^3}{\in_0r^2}$

Question 2

A disc rotates about its axis of symmetry in a horizontal plane at a steady rate of 3.5 revolutions per second. A coin placed at a distance of 1.25 cm from the axis of rotation remains at rest on the disc. The coefficient of friction between the coin and the disc is: (g = 10 m/s²)

Accepted Answer

0.6

Answer

0.7

Answer

0.5

Answer

0.3

Question 3

A body takes 10 minutes to cool from $60^\circ C$ to $50^\circ C$. The temperature of surroundings is constant at $25^\circ C$. Then, the temperature of the body after next 10 minutes will be approximately :

Accepted Answer

$43^\circ C$

Answer

$47^\circ C$

Answer

$41^\circ C$

Answer

$45^\circ C$

Question 4

Truth table for the following digital circuit will be :

Accepted Answer

XyZ001011101111

Answer

XyZ000010100111

Answer

XyZ000011101111

Answer

XyZ001011101110

Question 5

A capacitor $C_1 = 1.0 \mu F$ is charged up to a voltage $V = 60$ V by connecting it to battery B through switch (1). Now $C_1$ is disconnected from battery and connected to a circuit consisting of two uncharged capacitors $C_2 = 3.0 \mu F$ and $C_3 = 6.0 \mu F$ through switch (2), as shown in the figure. The sum of final charges on $C_2$ and $C_3$ is :

Accepted Answer

40 $\mu C$

Answer

20 $\mu C$

Answer

36 $\mu C$

Answer

54 $\mu C$