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Punjab Physics 2017 Paper 1 — Solved Past Paper with Answers
All 16 MCQs from Punjab Physics 2017 Paper 1, solved with the correct answer highlighted and a full explanation for every question. This is a free MDCAT Punjab / UHS past paper — no signup, no ads. Practise it interactively in timed mode, drill more with free MDCAT MCQs, or browse all Punjab / UHS papers.
Attempt this paper interactively →Q1. The electric field intensity due to an infinite sheet of charge is:
- A. Option A
- B. Option B
- C. Option C
- D. Option D✓
Explanation: Explanation will be added soon!
Q2. Thermo-couple converts heat energy into:
- A. Atomic energy
- B. Solar energy
- C. Electrial energy✓
- D. Nuclear energy
Explanation: Thermocouples convert heat energy into electrical energy. This is achieved through the Seebeck effect, where a temperature difference between two dissimilar metals generates a voltage that can be used to power electrical devices.
Why the other options are wrong
- A. Atomic energy refers to the energy released from nuclear reactions within an atom's nucleus, such as nuclear fission or fusion. Thermocouples do not convert heat energy into atomic energy.
- B. Solar energy is the energy derived from the Sun's radiation. Thermocouples do not directly convert heat energy into solar energy.
- D. Nuclear energy is the energy released from the nucleus of an atom during nuclear reactions.
Q3. If the number of turns become double but length remain same, then magnetic field in the solenoid become.
- A. Zero
- B. Remain same
- C. Half
- D. Double✓
Explanation: When the number of turns in a solenoid is doubled while the length remains the same, the magnetic field inside the solenoid becomes double its original value. This is because the magnetic field inside a solenoid is directly proportional to the number of turns per unit length.
Why the other options are wrong
- A. If the number of turns in a solenoid becomes double but the length remains the same, the magnetic field inside the solenoid does not become zero. Instead, it increases.
- B. This is incorrect. When the number of turns in a solenoid is doubled while the length remains the same, the magnetic field inside the solenoid doubles as well.
- C. This is also incorrect. Doubling the number of turns in a solenoid while keeping the length the same does not cause the magnetic field to become half of its original value. Instead, it doubles.
Q4. The SI unit of "B" is tesla which is equal to:
- A. NA-2m-2
- B. NA-2m-1
- C. NA-1m-2
- D. NA-1m-1✓
Explanation: NA-1m-1 is the correct unit for magnetic field strength. It combines the units of electric current (amperes, A) and length (meters, m) in a way that corresponds to the definition of magnetic field strength (force per unit current per unit length).
Why the other options are wrong
- A. This unit doesn't make sense in the context of magnetic field strength. It combines the units of electric charge (coulombs, C) and area (square meters, m2) in a way that doesn't relate to magnetic field.
- B. This unit is also incorrect. It combines the units of electric charge (coulombs, C) and length (meters, m) in a way that doesn't relate to magnetic field.
- C. This unit doesn't make sense for magnetic field strength. It combines the units of electric charge (coulombs, C) and area (square meters, m2) in a way that doesn't relate to magnetic field.
Q5. The emf produced by an alternating current generator is:
- A. NwAB sinθ✓
- B. NwAB cosθ
- C. NwAB sin2θ
- D. NwAB cos2θ
Explanation: NwAB sinθ is the correct expression for the emf. It represents the product of the number of turns in the coil (N), the angular frequency of the magnetic field (w), the area of the coil (A), the magnetic field strength (B), and the sine of the angle between the normal to the coil and the magnetic field (θ). This expression correctly represents the emf induced in the coil.
Why the other options are wrong
- B. This expression is incorrect because it uses the cosine function instead of the sine function. The correct expression for the emf involves the sine function, not the cosine function.
- C. This expression is incorrect because it uses the sine squared function (sin2θ) instead of the sine function. The correct expression for the emf involves the sine function, not the squared sine function.
- D. This expression is incorrect because it uses the cosine squared function (cos2θ) instead of the sine function. The correct expression for the emf involves the sine function, not the squared cosine function.
Q6. In D.C generator, split rings act as:
- A. Capacitor
- B. Commutator✓
- C. Inductor
- D. Resistor
Explanation: The commutator is a rotary electrical switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit.
Why the other options are wrong
- A. The split rings in a DC generator do not act as a capacitor. A capacitor is a passive two-terminal electrical component that stores energy in an electric field.
- C. The commutator is a rotary electrical switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit.
- D. The split rings in a DC generator do not act as a resistor. A resistor is a passive two-terminal electrical component that resists the flow of current.
Q7. The F.M transmission frequencies range from:
- A. 88Hz to 108Hz
- B. 88KHz to 108KHz
- C. 88MHz to 108MHz
- D. 88GHz to 108GHz✓
Explanation: FM transmission in the GHz (gigahertz) range is typically used for specialized applications such as satellite communications and radar systems. This range offers higher bandwidth and data transmission rates compared to lower frequency ranges, making it suitable for certain high-frequency applications.
Why the other options are wrong
- A. This range is too low for FM transmission, which operates in the MHz and GHz ranges, not the Hz range.
- B. This range is also too low for FM transmission. FM radio stations typically operate in the MHz range, not the kHz range.
- C. While the frequency range mentioned in option C is commonly associated with FM radio broadcasting, it is not the complete or accurate range. FM radio stations are allocated frequencies in the VHF (Very High Frequency) band, which extends from 30 MHz to 300 MHz. The range from 88 MHz to 108 MHz falls within this VHF band and is specifically designated for FM radio broadcasting.
Q8. When 10V are applied to an A.C circuit, the current flowing in it is 100mA. Its impedance is:
- A. 100Ω✓
- B. 10Ω
- C. 1000Ω
- D. 1Ω
Explanation: This option correctly calculates the impedance using Ohm's Law for AC circuits, which includes both resistance and reactance if present. The calculation is (frac{10V}{0.1A} = 100Ω), indicating that the impedance of the circuit is 100Ω.
Why the other options are wrong
- B. This option suggests that the impedance of the circuit is equal to the resistance, which is not accurate for an AC circuit. In an AC circuit, impedance is a combination of resistance and reactance, so the impedance is generally greater than just the resistance value.
- C. This option overestimates the impedance of the circuit. The correct calculation shows that the impedance is 100Ω, not 1000Ω.
- D. This option underestimates the impedance of the circuit. The correct calculation shows that the impedance is 100Ω, not 1Ω.
Q9. The critical temperature for aluminium as superconductor is:
- A. 7.2 K
- B. 1.18 K✓
- C. 4.2 K
- D. 3.72 K
Explanation: This is the approximate critical temperature for aluminum as a superconductor. Below this temperature, aluminum can exhibit superconducting properties.
Why the other options are wrong
- A. This temperature is significantly higher than the actual critical temperature of aluminum. Superconductivity typically occurs at much lower temperatures, close to absolute zero.
- C. While 4.2 K is a common critical temperature for another superconductor, niobium, it is not the critical temperature for aluminum. Aluminum's critical temperature is lower, around 1.18 K.
- D. This temperature is not the critical temperature for aluminum as a superconductor. The actual critical temperature for aluminum is closer to 1.18 K.
Q10. Photo diode is used for detection of:
- A. Heat
- B. Magnet
- C. Current
- D. Light✓
Explanation: Photodiodes are used for the detection of light. When light falls on a photodiode, it generates a current, which can be measured and used for various applications such as light sensing, optical communication, and light measurement.
Why the other options are wrong
- A. Photodiodes are not designed to detect heat. They are semiconductor devices that are specifically used for detecting light. When light strikes the photodiode, it generates a flow of current, but this is in response to the light, not heat.
- B. Photodiodes do not detect magnets. They are designed to convert light into an electrical current. Magnets are detected using devices like magnetometers, which are sensitive to magnetic fields.
- C. While it's true that photodiodes produce a current in response to light, they are not used to detect current in a circuit. Photodiodes are primarily used as light sensors, converting optical signals into electrical signals.
Q11. The number of terminals in a semiconductor diode are:
- A. 2✓
- B. 3
- C. 4
- D. 5
Explanation: A semiconductor diode has two terminals, an anode (+) and a cathode (-). It is a two-terminal device that allows current to flow in one direction only.
Why the other options are wrong
- B. A three-terminal device would typically be a transistor, not a diode. Transistors have three terminals: the emitter, base, and collector.
- C. Four-terminal devices are usually more complex semiconductor components like FETs (Field Effect Transistors) or certain types of integrated circuits. A diode is a simpler two-terminal device.
- D. Five-terminal devices are even more complex and are not typically found in basic diodes. They may be seen in advanced semiconductor devices like certain types of ICs (Integrated Circuits).
Q12. When an electron combines with a positron, we gain:
- A. One photon
- B. Three photons
- C. Two photons✓
- D. Four photons
Explanation: When an electron and a positron collide, they annihilate each other, and their mass is converted into energy in the form of two photons.
Why the other options are wrong
- A. The annihilation of an electron and a positron results in the production of two photons, not one.
- B. The annihilation of an electron and a positron produces two photons, not three.
- D. The annihilation of an electron and a positron results in the production of two photons, not four.
Q13. The compton shift in wavelength will be maximum when angle of scattering is:
- A. 90°
- B. 45°
- C. 180°✓
- D. 30°
Explanation: When the photon is scattered directly backward (180°), the Compton shift in wavelength is maximum. This is because the photon transfers the maximum amount of energy to the recoiling electron.
Why the other options are wrong
- A. At a 90° angle of scattering, the Compton shift is not maximum. Maximum shift occurs at 180°.
- B. The Compton shift is not maximum at a 45° angle of scattering. It is maximum at 180°.
- D. At a 30° angle of scattering, the Compton shift is not maximum. Maximum shift occurs at 180°.
Q14. For Paschen series, the value of "n" starts from:
- A. 2
- B. 4
- C. 6
- D. 8✓
Explanation: The Paschen series starts from n=3 and extends to higher values, with the lines corresponding to transitions to n=3 being in the infrared region.
Why the other options are wrong
- A. The series that starts from n=2 is the Balmer series, not the Paschen series.
- B. The Paschen series does not start from n=4. It starts from n=3.
- C. The Paschen series does not start from n=6. It starts from n=3.
Q15. Which of the following is similar to electron:
- A. β- Particle
- B. α — Particle✓
- C. Neutron
- D. Proton
Explanation: An alpha (α) particle consists of two protons and two neutrons bound together, which is similar to a helium-4 nucleus. Although an alpha particle is much more massive than an electron, both carry electric charge.
Why the other options are wrong
- A. A beta (β-) particle is similar to an electron in that they both have the same charge (-1) and similar mass. However, beta particles are high-energy electrons emitted from the nucleus of an atom during beta decay.
- C. A neutron is not similar to an electron because it is electrically neutral, unlike the electron, which carries a negative charge.
- D. A proton is not similar to an electron because it carries a positive charge, unlike the electron, which carries a negative charge.
Q16. The element formed by radioactive decay is called:
- A. Father element
- B. Mother element
- C. Parent element
- D. Daughter element✓
Explanation: This is the correct term for the element formed as a result of radioactive decay. It is the product of the decay process, derived from the parent element.
Why the other options are wrong
- A. This term is not typically used in the context of radioactive decay. It might be confusing because it could imply the original element, but the more commonly used term for this is the parent element.
- B. Similar to "father element," this term is not standard in the context of radioactive decay. It does not describe the original radioactive isotope.
- C. The parent element refers to the original radioactive isotope that undergoes decay to form a daughter element. However, in the context of the given question, "parent element" is not the correct answer choice.
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