Kpk Physics 2012 — Solved MCQs

Question 1

The energy stored in a charged capacitor is:

Accepted Answer

B. 1/2 CV2 — The energy (U) stored in a charged capacitor is given by the formula: U=1/2​CV2Where:C is the capacitance of the capacitor.V is the voltage across the capacitor.So, the correct option will be 1/2 CV². This formula tells us that the energy stored in a capacitor is directly proportional to the square of the voltage across it and the capacitance of the capacitor itself.

Question 2

Ohm's Law is mathematically written as:

Accepted Answer

C. V = IR — Ohm’s Law is mathematically written as: V = IRwhere:V is the voltage across the conductor (in volts),I is the current through the conductor (in amperes), andR is the resistance of the conductor (in ohms).

Question 3

Temperature coefficient of resistance of a conductor is _.

Accepted Answer

B. d= R0 - Rt / R0t — The temperature coefficient of resistance (often denoted as α) is a measure of how the resistance of a conductor changes with temperature. The formula for the temperature coefficient of resistance is given by: d= R0 - Rt / R0twhere:R0 is the resistance of the conductor at the reference temperature (usually 0°C or 20°C),Rt is the resistance of the conductor at temperaturet is the change in temperature from the reference temperature.This formula allows us to calculate how much the resistance of a conductor will change for a given change in temperature.

Question 4

In C.R.O, the time base circuit is connected to the _.

Accepted Answer

D. x-plates — In a Cathode Ray Oscilloscope (C.R.O), the time base circuit is typically connected to the horizontal deflection plates, also known as the X-plates. This connection allows for a time-varying voltage to be applied to these plates, causing the electron beam to be deflected horizontally at a uniform rate.

Question 5

For step-down transformer:

Accepted Answer

A. Np > Ns — For a step-down transformer, the primary voltage is higher than the secondary voltage (Vp > Vs), and the primary coil has more turns than the secondary coil (Np > Ns).

Question 6

The root-mean-square value of A.C current is given by Irms=

Accepted Answer

C. Im / √2 — The root-mean-square (RMS) value of an alternating current (AC), denoted as "Irms"​ & is given by the formula: Irms​ = Im / √2​whereIm​ is the peak or maximum current.

Question 7

The average power dissipated in one cycle in a capacitor is:

Accepted Answer

A. P = 0 — The average power dissipated in a capacitor over one complete cycle of alternating current (AC) is zero.This is because a capacitor in an AC circuit alternately stores and releases energy. During one half of the cycle, it stores energy as the voltage increases. During the other half of the cycle, it releases this energy as the voltage decreases.However, no power is lost (or dissipated) in this process because the energy is returned to the circuit, not converted into another form such as heat. Therefore, the average power dissipated over one complete cycle is zero.This is represented mathematically as: Pavg ​= 0

Question 8

The unit of volumetric stain is:

Accepted Answer

C. no unit — Volumetric strain is a dimensionless quantity and therefore, it does not have a specific unit. It is def.ined as the change in volume per unit volume due to an applied force or pressure.

Question 9

When N-type materials are required, then from which group impurities are added to Ge or Si?

Accepted Answer

D. 5th Group — N-type semiconductors are created when pure semiconductors, such as Silicon (Si) or Germanium (Ge), are doped with impurities from Group 5 of the periodic table. These impurities, also known as donor impurities & have five valence electrons.Examples of pentavalent impurities used for creating N-type semiconductors include Phosphorus (P), Arsenic (As) etc.

Question 10

When a body moves with speed nearly equal to speed of light then the effect on mass will

Accepted Answer

B. increase — When a body moves with a speed nearly equal to the speed of light, its mass is observed to increase. This is a result of the theory of special relativity.The increase in mass is negligible at everyday speeds, but as the speed of the object approaches the speed of light, its observed mass becomes infinitely large.

Question 11

The energy of photon E=

Accepted Answer

A. hf — The energy of a photon can be calculated using the equation: E=h⋅fwhere:E is the energy of the photon,h is Planck’s constant (approximately 6.62607015×10−34 joule seconds)f is the frequency of the photon.

Question 12

In a nuclear reaction, a beam of alpha particles strikes a target of Ni60. The product of this reaction might be:

Accepted Answer

C. Cu63 + H1 — In a nuclear reaction where a beam of alpha particles strikes a target of (Ni60), the product of this reaction can be determined by considering the properties of alpha particles and the nickel isotope. Alpha particles are essentially helium nuclei, which means they consist of 2 protons and 2 neutrons (He4).When an alpha particle collides with a nickel nucleus, a nuclear transmutation occurs, leading to the formation of a new element "Cu63 + H1"

Question 13

Light amplification by stimulated emission of radiation means:

Accepted Answer

A. laser — “Light Amplification by Stimulated Emission of Radiation” is the full form of the acronym LASER. It is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.

Question 14

G.M counter is based on phenomenon of production of ions in a _ medium by incident radiations.

Accepted Answer

C. gaseous — The Geiger-Muller (G.M) counter is based on the phenomenon of production of ions in a gaseous medium by incident radiations. When ionizing radiation passes through the gas in the G.M counter, the molecules of the gas are ionized, resulting in the gas containing free electrons and positive ions.

Question 15

Energy stored in a charged capacitor is given by

Accepted Answer

C. 1/2 CV2 — The energy (U) stored in a charged capacitor is given by the formula: U=1/2​CV2Where:C is the capacitance of the capacitor.V is the voltage across the capacitor.So, the correct option will be 1/2 CV². This formula tells us that the energy stored in a capacitor is directly proportional to the square of the voltage across it and the capacitance of the capacitor itself.

Question 16

In direction of induced e.m.f readily predicted by

Accepted Answer

D. Lenz law — The direction of induced electromotive force (e.m.f) can be predicted by Lenz’s Law. It states that the induced current due to the induced e.m.f always flows in such a direction as to oppose the change causing it. This means that the induced e.m.f and the resulting current flow should make the coil behave like a magnet that opposes the change in magnetic flux.

Question 17

The cyclotron frequency of an electron projected with a velocity 'V' perpendicular to the magnetic field 'B' is given by

Accepted Answer

D. f = 2π e/m x B — The cyclotron frequency (also known as gyrofrequency) of a charged particle moving perpendicular to a magnetic field is given by the formula: f = 2π e/m x B Here:f is the cyclotron frequency,e is the charge of the electron,m is the mass of the electron, andB is the magnetic field strength.This formula tells us that the frequency of the circular motion of a charged particle in a magnetic field is directly proportional to the strength of the magnetic field and inversely proportional to the mass of the particle. It’s independent of the velocity of the particle. This principle is used in cyclotron particle accelerators to accelerate charged particles to high energies.

Question 18

The color of light emitted by 'LED' depends upon

Accepted Answer

D. Type of semi-conductor — The color of light emitted by an LED (Light Emitting Diode) primarily depends on the type of semiconductor material used in the diode. When an electric current is applied, the energy band gap of the semiconductor material determines the wavelength of the light emitted, which in turn determines the color of the light.The other factors such as the amount of forward current, the reverse bias, and the forward bias, can influence the intensity and efficiency of the light emitted, but they do not directly determine the color of the light. Therefore, the correct answer is Type of semiconductor.

Kpk Physics 2012 — Solved Past Paper with Answers

More KPK / ETEA Solved Papers