Punjab Physics 2016 — Solved MCQs

Question 1

The open loop gain of amplifier is of the order of:

Accepted Answer

A. 105 — This means a gain of 100,000. This level of gain is high and is commonly found in many general-purpose operational amplifiers used in various electronic circuits.

Question 2

We can find from de Broglie formula:

Accepted Answer

A. Wavelength — The de Broglie formula directly calculates the wavelength of a particle based on its momentum. This wavelength is associated with the particle's wave-like behavior, as described by wave-particle duality in quantum mechanics.

Question 3

Energy of black body radiation depends upon:

Accepted Answer

D. Temperature of the body — The energy of black body radiation is directly proportional to the temperature of the body. As the temperature increases, the amount of radiation emitted by the body increases, and the peak wavelength of the radiation shifts to shorter wavelengths (higher frequencies), as described by Wien's displacement law.

Question 4

The following gas was identified in the sun using spectroscopy:

Accepted Answer

D. Nitrogen — Explanation will be added soon!

Question 5

When γ-rays are emitted, the nuclear mass:

Accepted Answer

B. Does not change — When γ-rays are emitted, the nuclear mass remains the same because γ-rays are electromagnetic radiation, not particles with mass.

Question 6

Which of the followings are not hadrons?

Accepted Answer

A. Muons — Muons are not hadrons. They are a type of lepton, which are particles that do not experience the strong nuclear force. Hadrons, on the other hand, are particles that are affected by the strong nuclear force, such as protons, neutrons, and mesons.

Question 7

Selenium is a:

Accepted Answer

B. Photoconductor — Semiconductors are materials that have electrical conductivity between that of conductors and insulators. Selenium falls into this category and is used in various electronic devices.

Question 8

Capacitance of a capacitor does not depend upon:

Accepted Answer

C. Electric field between plates — The capacitance of a capacitor does not depend on the electric field between the plates. The electric field is determined by the voltage applied to the capacitor and the distance between the plates, but it does not affect the capacitance itself.

Question 9

Kirchhoff's voltage rule is a way of stating conservation of:

Accepted Answer

A. Energy — Kirchhoff's voltage rule, also known as Kirchhoff's second law or the loop rule, is a statement of the conservation of energy in electrical circuits. It states that the total voltage around any closed loop in a circuit is equal to the sum of the voltage drops within that loop.

Question 10

If F1 and F2 are forces acting on α — Particle and electron respectively, when moving perpendicular to the magnetic field, then:

Accepted Answer

B. F1> F2 — The force experienced by a charged particle moving perpendicular to a magnetic field is given by the formula F = qvB, where q is the charge of the particle, v is its velocity, and B is the magnetic field strength. Since the charge of an α-particle (2e) is greater than the charge of an electron (e), the force experienced by the α-particle (F₁) would be greater than the force experienced by the electron (F₂).

Question 11

Which of the following is not accurate measuring device?

Accepted Answer

C. Potentiometer — A potentiometer is not typically considered a primary measuring device. It is used to manually adjust voltage levels in a circuit or as a variable resistor. While it can be used for measurement purposes in some configurations, it is not as precise or commonly used as the other options listed.

Question 12

Self inductance does not depend upon:

Accepted Answer

B. Area of cross-section of the core — The self-inductance of a coil does not depend on the area of cross-section of the core. The self-inductance is primarily determined by the geometry of the coil (number of turns, length of the coil, and diameter of the coil) and the permeability of the core material.

Question 13

Efficiency of transformer is not affected by:

Accepted Answer

A. Input voltage — The efficiency of a transformer is not directly affected by the input voltage. Efficiency is determined by the ratio of output power to input power, and variations in input voltage do not affect this ratio as long as the transformer is operating within its designed voltage range.

Question 14

In RLC series circuit at resonance the phase difference between capacitor and inductor reactances is:

Accepted Answer

C. 0° — At resonance, the reactance of the capacitor cancels out the reactance of the inductor, leaving only the resistance in the circuit. This results in a purely resistive impedance, and the phase difference between the capacitor and inductor voltages is 0°.

Question 15

Electrons vibrating 94,000 times each second will produce radio waves of frequency?

Accepted Answer

D. 94 KHz — The frequency of the vibrating electrons is 94,000 times per second, which is 94,000 Hz or 94 kHz. Radio waves typically range from about 3 kHz to 300 GHz, so a frequency of 94 kHz falls within the radio wave range.

Question 16

Which of the followings does not undergo plastic deformation?

Accepted Answer

C. Lead — Lead does not undergo plastic deformation to a significant extent. It is a soft metal with low tensile strength and is more likely to undergo elastic deformation or fracture under stress rather than plastic deformation.

Question 17

The gain of transistor amplifier depends upon?

Accepted Answer

B. Resistance connected at base — The gain of a transistor amplifier is significantly influenced by the resistance connected at the base. The base resistor sets the base current, which in turn controls the collector current and the amplification factor of the transistor.

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