Practice problems on NEET, NEET 2017

Question 1

A potentiometer is an accurate and versatile device to make electrical measurements of E.M.F, because the method involves :

Accepted Answer

A condition of no current flow through the galvanometer

Answer

Cells

Answer

Potential gradients

Answer

A combination of cells, galvanometer and resistances

Question 2

A gas mixture consists of 2 moles of O2​ and 4 moles of Ar at temperature T. Neglecting all vibrational modes, the total internal energy of the system is:

Accepted Answer

11RT

Answer

4RT

Answer

15RT

Answer

9RT

Question 3

Radioactive material 'A' has decay constant '8λ′  and material 'B' has decay constant ' λ  '. Initially they have same number of nuclei. After what time, the ratio of number of nuclei of material 'B' to that 'A' will be e1​  ?

Accepted Answer

7λ1​

Answer

λ1​

Answer

8λ1​

Answer

9λ1​

Question 4

A∪  tube with both ends open to the atmosphere, is partially filled with water. Oil, which is immiscible with water, is poured into one side until it stands at a distance of 10 mm  above the water level on the other side. Meanwhile the water rises by65 mm  from its original level (see diagram). The density of the oil is:

Accepted Answer

928 kg m−3

Answer

650 kg m−3

Answer

425 kg m−3

Answer

800 kg m−3

Question 5

A 250 -Turn rectangular coil of length 2.1 cm  and width 1.25 cm  carries a current of 85μA  and subjected to a magnetic field of strength 0.85 T. Work done for rotating the coil by 180∘ against the torque is:

Accepted Answer

9.1μJ

Answer

4.55μJ

Answer

2.3μJ

Answer

1.15μJ

Question 6

The de-Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature T (Kelvin) and mass m, is:

Accepted Answer

3mkT​h​

Answer

mkT​h​

Answer

3mkT​2h​

Answer

mkT​2h​

Question 7

One end of a string of length l is connected to a particle of mass ' m ' and the other end is connected to a small peg on a smooth horizontal table. If the particle moves in circle with speed ′v′ ,  the net force on the particle (directed towards center) will be ( T represents the tension in the string):

Accepted Answer

T1​

Answer

T+lmv2​

Answer

T−lmv2​

Answer

Zero

Question 8

Figure shows a circuit contains three identical resistors with resistance R=9.0Ω each, two identical inductors with inductance L=2.0mH  each, and an ideal battery with emf ε=18 V . The current 'i 'through the battery just after the switch closed is:

Accepted Answer

2 A

Answer

2 mA

Answer

0.2 A

Answer

0 ampere

Question 9

The x and y coordinates of the particle at any time are x=5t−2t2  and y=10  t respectively, where x and y are in meters and t in seconds. The acceleration of the particle at t=2 s  is:

Accepted Answer

−4 m/s2

Answer

0

Answer

5 m/s2

Answer

−8 m/s2

Question 10

Suppose the charge of a proton and an electron differ slightly. One of them is -e, the other is (e+Δe).  If the net of electrostatic force and gravitational force between two hydrogen atoms placed at a distance d (much greater than atomic size) apart is zero, then Δe  is of the order of :[Given mass of hydrogen mh​=1.67×10−27 kg].

Accepted Answer

10−37C

Answer

10−20C

Answer

10−23C

Answer

10−47C

Question 11

Two rods A and B of different materials are welded together as shown in figure. Their thermal conductivities are K1​  and K2​. The thermal conductivity of the composite rod will be:

Accepted Answer

2K1​+K2​​

Answer

23(K1​+K2​)​

Answer

K1​+K2​

Answer

2(K1​+K2​)

Question 12

The diagrams below show regions of equipotentials.A positive charge is moved from A to B in each diagram.

Accepted Answer

In all the four cases the work done is the same.

Answer

Maximum work is required to move q in figure (c).

Answer

Minimum work is required to move q in figure (a).

Answer

Maximum work is required to move q in figure (b).

Question 13

The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is:

Accepted Answer

4

Answer

2

Answer

1

Answer

0.5

Question 14

Young's double slit experiment is first performed in air and then in a medium other than air. It is found that 8th   bright fringe in the medium lies where 5th   dark fringe lies in air. The refractive index of the medium is nearly:

Accepted Answer

1.78

Answer

1.25

Answer

1.59

Answer

1.69

Question 15

A particle executes linear simple harmonic motion with an amplitude of 3 cm . When the particle is at 2 cm  from the mean position, the magnitude of its velocity is equal to that of its acceleration. Then its time period in seconds is:

Accepted Answer

5​4π​

Answer

π5​​

Answer

2π5​​

Answer

3​2π​

Question 16

Thermodynamic processes are indicated in the following diagram.Match the following

Accepted Answer

P→c,Q→a,R→d,S→b

Answer

P→a,Q→c,R→d,S→b

Answer

P→c,Q→d,R→b,S→a

Answer

P→d,Q→b,R→a,S→c

Question 17

A capacitor is charged by a battery. The battery is removed and another identical uncharged capacitor is connected in parallel. The total electrostatic energy of resulting system.

Accepted Answer

Decreases by a factor of 2

Answer

Increases by a factor of 4

Answer

Remains the same

Answer

Increases by a factor of 2

Question 18

The photoelectric threshold wavelength of silver is 3250×10−10 m.  The velocity of the electron ejected from a silver surface by ultraviolet light of wavelength 2536×10−10 m  is:(Given h=4.14×10−15eVs  and c=3×108 ms−1 )

Accepted Answer

=6×105 ms−1

Answer

=0.6×106 ms−1

Answer

=61×103 ms−1

Answer

=0.3×106 ms−1

Question 19

A physical quantity of the dimensions of length that can be formed out of c, G and4πε0​e2​  is :[c is velocity of light, G is universal constant of gravitation and e is charge]

Accepted Answer

c21​[G4πε0​e2​]21​

Answer

c2[G4πε0​e2​]21​

Answer

c1​G4πε0​e2​

Question 20

Two cars moving in opposite directions approach each other with speed of 22 m/s and 16.5 m/s respectively. The driver of the first car blows a horn having a frequency 400 Hz. The frequency heard by the driver of the second car is [velocity of sound 340 m/s] .

Accepted Answer

448 Hz

Answer

350 Hz

Answer

361 Hz

Answer

411 H