Kpk Physics 2017 — Solved Past Paper with Answers

Q1. The strength of electric field is equal to _

• A. Electrostatic potential
• B. Electric potential
• C. Potential gradient✓
• D. Potential difference

Explanation: The strength of an electric field is equal to the potential gradient, or in other words, the rate of change of electric potential with respect to distance.

Q2. What will be the Electrical flux if the surface which is placed perpendicular to the electric field?

• A. Φ = EA1✓
• B. Φ=θ
• C. Φ=EAcosθ
• D. None of these

Explanation: If the surface is placed perpendicular to the electric field, the electrical flux through the surface will be maximized. In this scenario, the flux is given by the product of the electric field strength (\( E \)) and the area (\( A \)) of the surface:\[ \text{Electrical flux} = E \cdot A \]Since the surface is perpendicular to the electric field, the angle between the electric field vector and the surface normal is \( 0^\circ \), resulting in maximum flux.

Q3. Which one of the given is a vector quantity?

• A. E flux
• B. Electrostatic potential
• C. Electric field intensity✓
• D. both A and C

Explanation: Electric field intensity and electrical flux are indeed vector quantities. They both have magnitude and direction associated with them.

Q4. The current in 2 Ω resistor is equal to _

• A. 1.23 A
• B. 0.73 A
• C. 1.29 A
• D. 1 A✓

Explanation: Explanation will be added later

Q5. Ampere's law is applicable to _

• A. Any closed path✓
• B. Circular path
• C. Rectangular path
• D. None of these

Explanation: Ampère's law is applicable to any closed path, regardless of its shape. Whether it's a circular path, a rectangular path, or any other closed loop, Ampère's law can be used to calculate the magnetic field around the loop as long as it encloses the current-carrying conductor or current-carrying region.

Q6. The magnetic flux will be maximum for an angle of _

• A. 180˚
• B. 90˚
• C. 60˚
• D. 0˚✓

Explanation: The magnetic flux through a surface is maximum when the magnetic field lines are perpendicular to the surface. In other words, the angle between the magnetic field vector and the surface normal should be 0∘. Therefore, the magnetic flux will be maximum for an angle of 0∘

Q7. A high voltage in a TV receiver is 17 KV and the Max allowable current is 150 μA. The least permissible value of load resistance is _

• A. 3.3 x 105 Ω
• B. 113.3 x 106 Ω✓
• C. 1
• D. 0

Explanation: The least permissible value of load resistance can be calculated using Ohm’s law, which states that the voltage across a resistor is equal to the current through it times its resistance. Mathematically, it is represented as: V=I×RWhere:V is the voltage (in volts)I is the current (in amperes)R is the resistance (in ohms)Rearranging the formula to find the resistance gives: R=IV​Substituting the given values into the formula:V = 17 KV = 17000 VI = 150 μA = 0.00015 AWe get: R = 17000​/0.00015 = 113.3 x 106 Ω

Q8. Which of the given induced emf is statistically induced emf?

• A. Dynamo
• B. Alternator
• C. AC Generator
• D. Transformer✓

Explanation: The statistically induced EMF is typically associated with a transformer.

Q9. Eddy current is produced when _

• A. A metal is exposed to changing magnetic field✓
• B. A metal is kept steady in magnetic field
• C. A circular cell is placed in steady Magnetic filed
• D. Current is passed through a coil

Explanation: These currents are caused by electromagnetic induction. Therefore, eddy currents are produced when conductive materials are subjected to changing magnetic fields.

Q10. Electromagnetic theory of relationship between charges, Circuits and electric and magnetic field was given by _

• A. Faraday
• B. Einstein
• C. Ampere
• D. Maxwell✓

Explanation: The electromagnetic theory that describes the relationship between charges, circuits, and electric and magnetic fields was primarily formulated by James Clerk Maxwell

Q11. What will be the strain if a wire is stretched to double its length?

• A. 0.5
• B. 0
• C. 1✓
• D. 2

Explanation: Strain=ΔL​/LIf a wire is stretched to double its original length, it means the change in length is equal to the original length (L). Therefore:Strain=2L−L/L=1

Q12. The material in which the valance band is completely filled is known _

• A. Semi conductor
• B. Conductor
• C. Insulator✓
• D. Super conductor

Explanation: The material in which the valence band is completely filled is known as an insulator

Q13. An addition of impurity into intrinsic _ is called doping

• A. Conductor
• B. Super conductor
• C. Semi conductor✓
• D. All of these

Explanation: An addition of impurity into intrinsic semiconductors is called doping.

Q14. Pair production occurs only when energy of photon is at least equal to _

• A. 1.02 GeV
• B. 1.02 MeV✓
• C. 1.02 eV
• D. 1.02 KeV

Explanation: Pair production occurs only when the energy of a photon is at least equal to twice the rest energy of an electron, which is equivalent to 2mec2 where me​ is the mass of the electron and ccc is the speed of light. This energy is approximately 1.02 MeV

Q15. Which one of the give is Balmer formula?

• A. 1/π = R (1/22 - 1/n2)
• B. 1/π = R (1 - 1/n2)✓
• C. 1/π = R (1/32 - 1/n2)
• D. None of these

Explanation: The Balmer formula is given by:1/π = R (1 - 1/n2)

Q16. A radioactive substance has a half-life of four months 3/4 th of the substance will decay in _

• A. 16 month
• B. 12 month✓
• C. 8 months
• D. 0 months

Explanation: 3/4 of the substance will decay in 12 months, which is three times the half-life.

Q17. A binding energy for nucleus A is 7.7 MeV and for nucleus B is 7.8 MeV. Which nucleus has the larger mass?

• A. Nucleus B✓
• B. Nucleus A
• C. Both has same mass
• D. None of these

Explanation: nucleus B has a higher binding energy per nucleon, it implies that the nucleons in nucleus B are more tightly bound than those in nucleus A.

Q18. The phase difference between current and voltage at resonance is

• A. π/2
• B. -π
• C. π
• D. 0✓

Explanation: For a series resonance, the phase difference is 0 degree