Punjab Physics 2015 Paper 2 — Solved MCQs

Question 1

Electron-volt is the unit of:

Accepted Answer

B. Electric energy — An electron-volt (eV) is a unit of energy equal to the energy gained or lost by an electron when it moves across an electric potential difference of one volt. It is commonly used in atomic and nuclear physics to express energy on the atomic and subatomic scale.

Question 2

Coulomb's electrostatic force is:

Accepted Answer

B. Conservative force — Coulomb's electrostatic force is a conservative force. This means that the work done by the electrostatic force on a charged particle moving between two points is independent of the path taken and depends only on the initial and final positions of the particle

Question 3

In case of colour code for carbon resistance, tolerance for silver band is:

Accepted Answer

C. ±10% — This tolerance is not a standard tolerance for carbon resistors in the color code system. The closest standard tolerance to ±6% is ±5% (gold band) or ±10% (silver band).

Question 4

The galvanometer can be made sensitive by making the factor a C/BAN:

Accepted Answer

B. Small — A galvanometer can be made more sensitive by making the factor C/BAN (coil turns/magnetic field strength) smaller. This means increasing the sensitivity of the galvanometer by either increasing the number of coil turns or decreasing the magnetic field strength.

Question 5

The S.I unit of magnetic flux is:

Accepted Answer

A. NmA-1 — The SI unit of magnetic flux is the weber (Wb), which is equivalent to volt-seconds (V·s) or tesla square meters (T·m²).

Question 6

Lenz's law is in accordance with the law of conservation of:

Accepted Answer

C. Energy — Lenz's law is in accordance with the law of conservation of energy. It states that the direction of the induced electromotive force (emf) or current is always such that it opposes the change in magnetic flux that produced it. This opposition results in the dissipation of energy as heat in the conductor.

Question 7

If back emf in a motor decreases, then it will draw:

Accepted Answer

B. More current — f the back emf decreases, the motor will draw more current to compensate for the decrease in the back emf. This increased current is necessary to maintain the power output and overcome any additional resistance in the circuit.

Question 8

The total reactance of RLC- series circuit at reasonce is:

Accepted Answer

A. Equal to resistance — At resonance in an RLC series circuit, the total reactance is equal to the resistance. At resonance, the inductive reactance (XL) is equal to the capacitive reactance (XC), and they cancel each other out, leaving only the resistance (R) as the total impedance of the circuit.

Question 9

Electromagnetic waves transport:

Accepted Answer

C. Energy — Electromagnetic waves transport energy through space. The energy carried by an electromagnetic wave is proportional to its frequency; higher frequency waves (such as X-rays and gamma rays) carry more energy than lower frequency waves (such as radio waves).

Question 10

The S.I unit of stress is:

Accepted Answer

D. Nm-2 — Nm-2 is the correct SI unit of stress. Stress is defined as force per unit area, and its SI unit is newtons per square meter (Nm⁻²), which is also known as pascal (Pa).

Question 11

In reverse biasing, p-n junction offers:

Accepted Answer

B. High resistance — In reverse biasing, the p-n junction offers high resistance to the flow of current. The reverse bias voltage increases the width of the depletion region, which inhibits the flow of majority carriers across the junction, resulting in high resistance.

Question 12

The value of potential barrier for silicon diode is:

Accepted Answer

A. 0.7 volt — While this value is close to the correct potential barrier for a silicon diode, the standard value is typically considered to be 0.7 volts. Some silicon diodes may have a slightly lower forward voltage drop, but 0.7 volts is a commonly used approximation for silicon diodes.

Question 13

If a material object moves with speed of light, its mass becomes:

Accepted Answer

C. Zero — According to the theory of relativity, as an object with mass approaches the speed of light, its relativistic mass increases without bound. At the speed of light, the relativistic mass would theoretically become infinite, but this is not physically achievable. The energy required to accelerate an object with mass to the speed of light would be infinite, making it impossible to reach that speed.

Question 14

Davisson-Germer confirmed the:

Accepted Answer

C. Dual nature of light — The Davisson-Germer experiment confirmed the dual nature of light, which is the idea that light exhibits both wave-like and particle-like properties. The experiment demonstrated the wave-like nature of electrons through electron diffraction, which is analogous to the diffraction of light waves.

Question 15

The diameter of an atom is of the order of:

Accepted Answer

A. 10-12m — This is the correct order of magnitude for the diameter of an atom. The typical size of an atom is on the order of 0.1 nanometers, which is equivalent to 10⁻¹² meters.

Question 16

The amount of energy equivalent to 1 a.m.u is:

Accepted Answer

C. 931.5MeV — This is the correct value. The energy equivalent of 1 amu is approximately 931.5 MeV (million electron volts). This value is derived from Einstein's mass-energy equivalence principle, E=mc², where E is energy, m is mass, and c is the speed of light in a vacuum. 1 amu is equivalent to approximately 931.5 million electron volts

Question 17

Natural radioactivity was discovered by:

Accepted Answer

A. H.Becquerel — Henri Becquerel discovered natural radioactivity in 1896. He accidentally discovered that uranium salts emitted rays that could fog a photographic plate, indicating the presence of a previously unknown form of radiation.

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