Competitive Exams: Physics MCQs (Practice-Test 10 of 35)

  1. The ratio of reverse-resistance to the forward-resistance of a good solid-state diode is about

    1. 10: 1

    2. 1: 10

    3. 1: 100

    4. 1: 1000

  2. For a BJT, the current amplification factor a = 0.9. This transistor is connected in CE configuration. When the base current changes by 0.4 mA, the change in collector current will be

    1. 36 mA

    2. 9 mA

    3. 4 mA

    4. 3.6 mA

  3. A CE amplifier has a voltage gain of 50, an input impedance of 1000 ohm, and an output impedance of 200 ohm. The power gain of the amplifier will be

    1. 24 dB

    2. 41 dB

    3. 250 dB

    4. 12500 dB

  4. The input signal given to a CE amplifier having a voltage gain of 150 is v1 = 2 cos (15t + 100) The corresponding output signal is

    1. 300 cos (15t + 190')

    2. 300 cos (15t + 90')

    3. 75 cos (15t + 10')

    4. 2 cos (15t + 190')

  5. Which one of the following logic gates does the given truth table represent? A B C 0 0 0 0 1 0 1 0 0 1 1 1

    1. NOT

    2. NOR

    3. OR

    4. AND

  6. The diagram of a logic circuit is given be-low: The output F of the circuit is represented by

    1. W (X + Y).

    2. W (X. Y).

    3. W + (X. Y)

    4. W + (X + Y)

    • Assertion (A): The angular momentum under a central force is constant.
    • Reason (R): Inverse square law of force is conservative.
    1. Both A and R are true and R is the correct explanation of A

    2. Both A and R are true but R is NOT the correct explanation of A

    3. A is true but R is false

    4. A is false but R is true

    • Assertion (A): Lorenz transformations are linear transformations.
    • Reason (R): The velocity of light is invariant in all inertial frames.
    1. Both A and R are true and R is the correct explanation of A

    2. Both A and R are true but R is NOT the correct explanation of A

    3. A is true but R is false

    4. A is false but R is true

    • Assertion (A): The upper surface of the wings of an aero plane is made convex and the lower surface is made concave.
    • Reason (R): The air currents at the top have a smaller velocity and thus less pressure at the bottom than at the top.
    1. Both A and R are true and R is the correct explanation of A

    2. Both A and R are true but R is NOT the correct explanation of A

    3. A is true but R is false

    4. A is false but R is true

    • Assertion (A): All the rain drops hit the surface of the earth with the same constant velocity.
    • Reason (R): An object falling through a viscous medium eventually attains a terminal velocity.
    1. Both A and R are true and R is the correct explanation of A

    2. Both A and R are true but R is NOT the correct explanation of A

    3. A is true but R is false

    4. A is false but R is true

    • Assertion (A): Experimental results indicate that the molar specific heat of hydrogen gas below 50 K is equal to 5/2R, where R is the universal gas constant.
    • Reason (R): A diatomic hydrogen molecule possesses three transnational and two rotational degrees of freedom.
    1. Both A and R are true and R is the correct explanation of A

    2. Both A and R are true but R is NOT the correct explanation of A

    3. A is true but R is false

    4. A is false but R is true

    • Assertion (A): The pressure exerted by a gas is the same and independent of the finite size of the molecules.
    • Reason (R): Molecular collisions will invariably change the velocities of individual molecules but the number of molecules having any particular velocity will remain unaltered.
    1. Both A and R are true and R is the correct explanation of A

    2. Both A and R are true but R is NOT the correct explanation of A

    3. A is true but R is false

    4. A is false but R is true

    • Assertion (A): With the help of a reversible engine it is possible to extract heat from a source and convert all of it into mechanical work.
    • Reason (R): Thermal energy and mechanical energy are different forms of energy.
    1. Both A and R are true and R is the correct explanation of A

    2. Both A and R are true but R is NOT the correct explanation of A

    3. A is true but R is false

    4. A is false but R is true

    • Assertion (A): Photoelectric effect can take place only with an electron bound in the atom.
    • Reason (R): Electron is a fermions, whereas proton is a boson.
    1. Both A and R are true and R is the correct explanation of A

    2. Both A and R are true but R is NOT the correct explanation of A

    3. A is true but R is false

    4. A is false but R is true