The efficiency of an ideal heat engine (Carnot heat engine) working between the freezing point and boiling point of water is:
1. \(26.8\%\) 2. \(20\%\)
3. \(6.25\%\) 4. \(12.5\%\)
Subtopic:  Carnot Engine |
 78%
Level 2: 60%+
NEET - 2018
Hints
Links

At what temperature will the \(\text{rms}\) speed of oxygen molecules become just sufficient for escaping from the earth's atmosphere? 
(Given: Mass of oxygen molecule \((m)= 2.76\times 10^{-26}~\text{kg}\), Boltzmann's constant \(k_B= 1.38\times10^{-23}~\text{J K}^{-1}\))
1. \(2.508\times 10^{4}~\text{K}\)
2. \(8.360\times 10^{4}~\text{K}\)
3. \(5.016\times 10^{4}~\text{K}\)
4. \(1.254\times 10^{4}~\text{K}\)

Subtopic:  Types of Velocities |
 65%
Level 2: 60%+
NEET - 2018
Hints
Links

A metallic rod of mass per unit length of \(0.5\) kgm–1 is lying horizontally on a smooth inclined plane which makes an angle of \(30^\circ\) with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction of \(0.25\) T is acting on it in the vertical direction. What is the current flowing through the rod to keep it stationary?
1. \(7.14\) A 2. \(5.98\) A
3. \(14.76\) A 4. \(11.32\) A
Subtopic:  Lorentz Force |
 59%
Level 3: 35%-60%
NEET - 2018
Hints
Links

advertisementadvertisement

An inductor of \(20~\text{mH}\), a capacitor of \(100~\mu \text{F}\), and a resistor of \(50~\Omega\) are connected in series across a source of emf, \(V=10 \sin (314 t)\). What is the power loss in this circuit?
1. \( 0.79 ~\text{W} \)
2. \( 0.43 ~\text{W} \)
3. \( 2.74 ~\text{W} \)
4. \( 1.13 ~\text{W}\)

Subtopic:  Power factor |
 56%
Level 3: 35%-60%
NEET - 2018
Hints
Links

A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy. The work required to do this comes from:

1. the current source
2. the magnetic field
3. the lattice structure of the material of the rod
4. the induced electric field due to the changing magnetic field.
Subtopic:  Magnetic Materials |
 55%
Level 3: 35%-60%
NEET - 2018
Hints
Links

The current sensitivity of a moving coil galvanometer is \(5~\text{div/mA}\) and its voltage sensitivity (angular deflection per unit voltage applied) is \(20~\text{div/V}.\) The resistance of the galvanometer is: 
1. \(40~\Omega\)
2. \(25~\Omega\)
3. \(250~\Omega\)
4. \(500~\Omega\)

Subtopic:  Moving Coil Galvanometer |
 72%
Level 2: 60%+
NEET - 2018
Hints
Links

advertisementadvertisement

If the mass of the sun were ten times smaller and the universal gravitational constant were ten times larger in magnitude, which of the following statements would not be correct?

1. Raindrops would drop faster.
2. Walking on the ground would become more difficult.
3. Time period of a simple pendulum on the earth would decrease.
4. Acceleration due to gravity \((g)\) on earth would not change.
Subtopic:  Acceleration due to Gravity |
 74%
Level 2: 60%+
NEET - 2018
Hints
Links

A solid sphere is in rolling motion. In rolling motion, a body possesses translational kinetic energy (Kt) as well as rotational kinetic energy (Kr) simultaneously. The ratio Kt : (Kt + Kr) for the sphere will be:

1. 7:10

2. 5:7

3. 10:7

4. 2:5

 79%
Level 2: 60%+
NEET - 2018
Hints
Links

The kinetic energies of a planet in an elliptical orbit around the Sun, at positions \(A,B~\text{and}~C\) are \(K_A, K_B~\text{and}~K_C\) respectively. \(AC\) is the major axis and \(SB\) is perpendicular to \(AC\) at the position of the Sun \(S\), as shown in the figure. Then:

1. \(K_A <K_B< K_C\)
2. \(K_A >K_B> K_C\)
3. \(K_B <K_A< K_C\)
4. \(K_B >K_A> K_C\)

Subtopic:  Kepler's Laws |
 80%
Level 1: 80%+
NEET - 2018
Hints
Links

advertisementadvertisement

A solid sphere is rotating freely about its axis of symmetry in free space. The radius of the sphere is increased keeping its mass the same. Which of the following physical quantities would remain constant for the sphere?

1. angular velocity
2. moment of inertia
3. rotational kinetic energy
4. angular momentum

Subtopic:  Angular Momentum |
 73%
Level 2: 60%+
NEET - 2018
Hints
Links