1. In a junction diode the holes are due to

Punjab PMET 2004 Semiconductor Electronics: Materials Devices And Simple Circuits

2. A torque of $10^{-5}$ Nm is required to hold a magnet at $90^\circ$ with the horizontal component of the earth's magnetic field. The torque required to hold it at $30^\circ$ will be

Bihar CECE 2010 Magnetism And Matter

3. A spherical portion has been removed from a solid sphere having a charge distributed uniformly in its volume as shown in the figure. The electric field inside the emptied space is

IIT JEE 2007 Electrostatic Potential And Capacitance

4. Consider the following statements A and Band identify the correct answer A : Thermistors can have only negative temperature coefficients of resistance B : Thermistors with negative temperature coefficients of resistance are used as resistance thermometers, to measure low temperature of the order of 10 K

EAMCET 2006 Electromagnetic Induction

5. The unit of universal gas constant is

Manipal 2008 Physical World, Units and Measurements

6. An object is placed at a distance of 12 cm from a convex lens on its principal axis and a virtual image of certain size is formed. If the object is moved 8 cm away from the lens, a real image of the same size as that of the virtual image is formed. The focal length of the lens is

JIPMER 2010 Ray Optics And Optical Instruments

7. In a step-up transformer, the turn ratio is 1 : 2. A Leclanche cell (emf = 1.5 V) is connected across the primary. The voltage developed in the secondary would be

JIPMER 2010 Alternating Current

8. Momentum of photon wavelength $λ$ is

AIPMT 1993 Dual Nature Of Radiation And Matter

9. A simple pendulum has time period $T_1$. The point of suspension is now moved upward according to the relation $y = kt^2, (k = 1m/s^2)$ where y is the vertical displacement. The time period now becomes T_2. The ratio of $\frac{T^2_1}{T^2_2}$ is $(Takeg = 10m/s^2)$

IIT JEE 2005 Oscillations

10. Two particles having mass M and m are moving in a circular path having radius R and r. If their time period are same then the ratio of angular velocity will be

AIPMT 2001 Motion In A Plane

KCET 2013 Atoms

12. A coin is placed on a horizontal platform which undergoes vertical simple harmonic motion of angular frequency $\omega$. The amplitude of oscillation is gradually increased. The coin will leave contact with the platform for the first time

AIIMS 2008 Oscillations

13. If the half-life of any sample of radioactive substance is 4 days, then the fraction of sample will remain undecayed after 2 days, will be

Rajasthan PMT 2007 Nuclei

14. Which of the following, when added as an impurity into the silicon produces n type semiconductor?

AIPMT 1999 Semiconductor Electronics: Materials Devices And Simple Circuits

15. An ideal gas is initially at temperature T and volume V.Its volume is increaseci by $\Delta$V due to an increase in temperature $\Delta$T, pressure remaining constant. The physical quantity$\delta =\frac{\Delta T}{V\Delta T}$ varies with temperature as

EAMCET 2010 Thermal Properties Of Matter

16. If force (F), velocity (V) and time (T) are taken as fundamental units, then the dimensions of mass are

AIPMT 2014 Physical World, Units and Measurements

17. To increase the angular width of interference fringes

COMEDK 2007 Wave Optics

18. A point mass of 1 kg collides elastically with a stationary point mass of 5 kg. After their collision, the 1 kg mass reverses its direction and moves with a speed of 2 ms ~ . Which of the following statement(s) is/are correct for the system of these two masses?

IIT JEE 2010 System Of Particles And Rotational Motion

19. A metro train starts from rest and in 5 s achieves 108 $kmh^{-1}$. After that it moves with constant velocity and comes to rest after travelling 45 m with uniform retardation. If total distance travelled is 395 m, find total time of travelling

Delhi UMET 2006 Motion In A Straight Line

20. There is current of 40 A in wire of $10^{-6}m^2$ area of cross-section. lf the number of free electrons per cubic metre is $10^{29}$, then the drift velocity is

BHU 2008 Electromagnetic Induction

21. The ratio of the maximum to the minimum wavelengths in Balmer series of H spectrum is

COMEDK 2008 Atoms

22. The coercivity of a small magnet where the ferromagnet gets demagnetised is $3\times {10}^3 Am^{-1}$ . The current required to be passed in a solenoid of length 10 cm and number of turns 100, so that the magnet gets demagnetised when inside the solenoid is

JEE Main 2014 Moving Charges And Magnetism

23. The radius of gyration of a rod of length Land mass M about an axis perpendicular to its length and passing through a point at a distance L/3 from one of its ends is

Punjab PMET 2008 System Of Particles And Rotational Motion

24. The density of a newly discovered planet is twice that of earth. The acceleration due to gravity at the surface of the planet is equal to that at the surface of the earth. If the radius of the earth is R, the radius of the planet would be

AIPMT 2004 Gravitation

25. When a weight of 10 kg is suspended from a copper wire of length 3 m and diameter 0.4 mm. Its length increases by 2.4 cm. lf the diameter of the wire is doubled, then the extension in its length will be

Bihar CECE 2010 Mechanical Properties Of Solids

26. Two coherent monochromatic; light beams of intensities $I$ and $4I$ are superposed. Intensities at constructive and· destructive interferenc positions will be

COMEDK 2005 Wave Optics

27. The temperature (T) dependence of resistivity (p) of a semiconductor is represented by

BHU 2010 Electromagnetic Induction

28. $n_1$ is the frequency of the pipe closed at one end and $n_2$ is the frequency of the pipe open at both ends. If both are joined end to end, find the fundamental frequency of closed pipe so formed

Maharashtra CET 2011 Electromagnetic Waves

29. A galvanometer can be converted into a voltmeter by connecting a

JIPMER 2014 Moving Charges And Magnetism

30. Two strings with mass per unit length of $25 \ g \ cm^{-1}$ and $9 \ gcm^{-1}$ are joined together in series. The reflection coefficient for the vibration waves are

Maharashtra CET 2006 Electromagnetic Waves