Laws and Principles MCQ Quiz - Objective Question with Answer for Laws and Principles - Download Free PDF

The correct answer is It depends on the length of the string.

Key Points

• The time period of a pendulum is defined as the time it takes for the pendulum to complete one full oscillation (swing back and forth).
• The time period of a simple pendulum is given by the formula: T = 2π√(L/g), where:
  • T is the time period.
  • L is the length of the string.
  • g is the acceleration due to gravity.
• From the formula, it is clear that the time period depends directly on the square root of the length of the string. As the length increases, the time period also increases.
• The time period is independent of other factors such as the mass of the bob or the material of the bob.
• Thus, the correct and most significant factor affecting the time period of a pendulum is the length of the string.

Additional Information

•  The three parts of a pendulum are
  • cable or wire
  • bob or weight,
  • fixed point
• The fixed point is the starting point of where the wire hangs from and the weight is what's attached to the wire or the endpoint of the wire.
• Depending on the length of the wire, the pendulum moves at a certain uniform speed.
• A hinge is a mechanical bearing that connects two solid objects, typically allowing only a limited angle of rotation between them.
• a round handle, or a small, round device for controlling a machine or electrical equipment.
• A brass doorknob turns/Twiddle the little knob to adjust the volume.

The correct option is an Air compressor

Key Points

• An air compressor is a heat engine that absorbs electricity.
• Air compressors work by forcing atmospheric air under pressure to create potential energy that can be stored in a tank for later use.
• The pressure builds up when the compressed air is deliberately released, converting the potential energy into usable kinetic energy

Additional Information

• A heat engine is used to produce mechanical energy by using heat energy as a source.
• Working:-
  • It uses fuel such as petrol or diesel and converts its chemical energy into thermal energy by burning it.
  • This thermal energy is then used to move mechanical parts, thus producing mechanical energy. This system is a thermodynamic system. 
• Types of heat engines.
• 1. Internal Combustion Engine (IC engines)
  • The burning of fuel, commonly known as combustion, occurs inside the system.
  •  An IC engine is a type of heat engine that uses working fuel such as petrol and diesel as a heat energy source.
  • The working principle is that it produces work by burning fuel and creating a high-pressure environment.
  • High pressure is then used to run a turbine or a piston, which converts the heat energy to mechanical energy.
  • Petrol engine or Spark-ignition engine: The basic principle is that a piston is moved up and down by burning the fuel using a spark.
  • Diesel engine or Compression ignition engine: It has the same principle as the spark-ignition engine. The only difference is that the fuel (diesel) is made to combust by producing high pressure. It is commonly used in heavy-duty vehicles.
• 2. External Combustion Engine
  • In this type, the burning of fuel, commonly known as combustion, takes place outside the system.
  • It is commonly known as EC engines.
  • In this engine, heat from the burnt fuel is transferred to a secondary liquid, which acts as fuel for the engine.
  • Examples: In the steam engine, the heat of combustion is employed to generate steam,
  • Steam is used in a reciprocating engine to produce useful work.

The correct answer is Electromagnetic Induction.

• The modern electrical generator works on the Electromagnetic Induction principle. 

Additional Information

• Faraday’s first law of electromagnetic induction states that whenever a conductor is placed in a varying magnetic field, emf is induced which is called induced emf. If the conductor circuit is closed, the current will also circulate through the circuit and this current is called induced current.
• Faraday's second law of electromagnetic induction states that the magnitude of emf induced in the coil is equal to the rate of change of flux that linkages with the coil. The flux linkage of the coil is the product of a number of turns in the coil and flux associated with the coil.

Important Points

• Electric generator function-
  • ​An Electric generator works on the principle of Faraday's law of Electromagnetic Induction.
  • An electric generator uses mechanical energy to generate electricity applying Faraday's law of induction.
  • It spins a coil at a constant rate in a magnetic field to induce an oscillating emf.
  • A conductor coil (a copper coil tightly wound onto a metal core) is rotated rapidly between the poles of a horseshoe-type magnet. The conductor coil along with its core is known as an armature.
  • The armature is connected to a shaft of a mechanical energy source such as a motor and rotated.
  • The mechanical energy required can be provided by engines operating on fuels such as diesel, petrol, natural gas, etc., or via renewable energy sources.
  • When the coil rotates, it cuts the magnetic field which lies between the two poles of the magnet.
  • The magnetic field will interfere with the electrons in the conductor to induce a flow of electric current inside it.

The correct answer is Pascal's Law.

Key Points

• Pascal's law states that when a pressure is applied to a confined fluid, the pressure change occurs throughout the fluid uniformly in all directions.
• Hydraulic systems like brakes, lifts, and presses function based on Pascal's law by transmitting applied force through an incompressible fluid.
• In hydraulic brakes, a small force applied at the brake pedal gets amplified by transmitting pressure through brake fluid to stop the vehicle effectively.
• Hydraulic lifts use Pascal's principle to lift heavy loads by applying force over a smaller area, which is then transmitted to a larger area.
• This principle is widely used in industries and machinery for efficient force multiplication.

Additional Information

• Pascal's Law Formula:
  • The formula is given by: P = F/A, where P is the pressure, F is the force applied, and A is the area.
  • This equation explains how force is transmitted through a fluid in hydraulic systems.
• Incompressible Fluid:
  • An incompressible fluid is a fluid whose density does not change significantly under pressure.
  • Hydraulic systems rely on such fluids for effective force transmission.
• Applications of Pascal's Law:
  • Hydraulic brakes in vehicles, where force from the brake pedal is transmitted to brake pads.
  • Hydraulic lifts used in construction and automotive industries to lift heavy objects.
  • Hydraulic presses used for shaping, compressing, or molding materials.
• Hydraulic Multiplier Effect:
  • Pascal's law enables a small force applied over a small area to generate a larger force over a larger area.
  • This principle is what makes hydraulic systems highly efficient for heavy-duty applications.

The correct answer is Evaporation.

Key Points

• The electrical appliance which keeps the object cool is called a refrigerator.
  • The refrigerator works on the Carnot cycle.
  • An ideal cycle that gives maximum possible efficiency is called the Carnot cycle.
  • The first refrigerator was built by John Gorrie in 1844.
  • The five basic parts of a refrigerator are an expansion valve, evaporator coils, compressor, Radiator pipes, and refrigerant.
  • The expansion valve lowers the temperature of the refrigerant by expanding it, and then it flows through the chilling cabinet, cooling it down.
  • The other components control the flow of refrigerant and radiate out the heat.
• The basic principle is that whenever a liquid coolant is passed through things at a higher temperature, it absorbs the heat; gets evaporated and the cooling effect is produced.
• The Refrigerator works on the principle of evaporation. So option 4 is correct.

The Correct Answer is Elasticity.

Key Points

• Elasticity is the ability of a deformed material body to return to its original shape and size when the forces causing the deformation are removed.
• A body with this ability is said to behave (or respond) elastically. 

Additional Information

• Fluid pressure is the pressure at a point within a fluid arising due to the weight of the fluid.
• Radioactivity is the process by which an unstable atomic nucleus loses energy by radiation.
• A material containing unstable nuclei is considered radioactive.
• Three of the most common types of decay are alpha decay, beta decay, and gamma decay, all of which involve emitting one or more particles or photons.

Explanation:

Kirchhoff's Law 

For an arbitrary body emitting and absorbing thermal radiation in thermodynamic equilibrium, the emissivity and absorptivity are equal. That means anybody absorbing heat well will also emit the heat energy well.  

The correct answer is Photo voltaic cells.

Key Points

• Solar technologies convert sunlight into electrical energy either through photovoltaic (PV) cells or through mirrors that concentrate solar radiation.
• This energy can be used to generate electricity or be stored in batteries or thermal storage.
• A solar cell, or photovoltaic cell, is a semiconductor device that converts the energy of light directly into electricity by the photovoltaic effect.
• Photovoltaic modules often have a sheet of glass on the sun-facing side, allowing light to pass while protecting the semiconductor wafers. 
• The photovoltaic effect was experimentally demonstrated first by French physicist Edmond Becquerel.

CONCEPT:

• Fleming's right-hand rule: if we extend the forefinger, middle finger, and the thumb of our right-hand perpendicular to each other as shown in the figure and the thumb pointing toward the conductor's motion and the forefinger pointing towards the magnetic field direction, the middle finger gives us the direction of the induced current flowing in the circuit.

So the correct answer is option 2.

​The correct answer is Coulomb’s Law.

Key Points

• Coulomb’s Law talks about the magnitude of the attraction between the two charges.
  • It says that the force is directly proportional to the product of the quantity of the two charges.
  • F ∝ q1q2, where (F is Force, q1 and q2 are charges).
  • It is also inversely proportional to the square of the distance between them.
• i.e., F ∝ 1/r2 where (F is Force, r is the distance between the charges).
• Thus, the equation is
• \(F\; = \;k\frac{{{q_1}{q_2}}}{{{r_2}}}\;\)where k is the proportionality constant and is equal to 9 × 109 Nm2/C2.
• The Law was given by Charles-Augustin de Coulomb in the year 1784.

Additional Information

• Lenz's law states that the direction of the induced current in the coil will be always in such a way that it opposes the change which produces the current.
• According to Gauss law, the total electric flux linked with a closed surface called Gaussian surface is \(\frac{1}{ϵ_o}\) the charge enclosed by the closed surface.
• Ohm’s law states that at a constant temperature, the current through a conductor between two points is directly proportional to the voltage across the two points.

The correct option is Newton's Third Law of Motion.

Key Points

Newton’s third law is the principle behind the working of a jet plane.
Newton’s Third Law of Motion:

• The Third Law states that, In every action, there is an equal and opposite reaction.
• ​When a man jumps out from a boat, he presses the boat with his feet, which means he is doing an action, and the boat then also exerts an equal force on him in the opposite direction which explains the reaction, therefore the man jumps to the bank and the boat moves in the backward direction.

Jet engines move the airplane forward with a great force that is produced by a tremendous thrust and causes the plane to fly very fast. All jet engines, which are also called gas turbines, work on the same principle. The engine sucks air in at the front with a fan. A compressor raises the pressure of the air.

Additional Information

Newton’s First Law of Motion:

• According to it, if a body is at rest will remain at rest, and the body is in motion will remain in motion unless an external force is applied to it.
• Example: The motion of a ball falling down through the atmosphere

Newtons Second Law:

• Newton's second law of motion is F = ma, where m is the mass of an object and a is the acceleration due to gravity.
• An example of Newton's 2nd law is Riding your bicycle.

Newtons Law of Gravitational constant

• Newton's law of gravitation states that everybody in the universe attracts every other body with a force, which is directly proportional to the product of their masses and inversely proportional to the square of the between their centers.
• The direction of force is along the line joining the particles.
• Then Gravitational force of attraction is given by
• \(F = \frac{{G{M_1}{M_2}}}{{{r^2}}}\)
• where G = universal gravitational constant, M₁ = Mass of the 1st body, M₂ = Mass of the 2nd  body, and R = Distance between the bodies 

The correct answer is option 2 i.e., The process is used for making nuclear bombKey Points

• A nuclear bomb uses either uranium or plutonium and relies on fission, a nuclear reaction in which a nucleus or an atom breaks into two pieces.
• The by-products of nuclear fission include free neutrons, photons usually in the form of gamma rays, and other atomic fragments such as beta particles and alpha particles.
• Nuclear fission produces energy for nuclear power and drives atomic weapon explosions.
• Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles (neutrons or protons).
• An example of nuclear fusion is the process of four hydrogens coming together to form helium.
• A hydrogen bomb is based on the principle of uncontrollable nuclear fusion.

The correct answer is Theory of relativity.

Key Points

• According to physicist Albert Einstein's theory of relativity, nothing in the universe can travel faster than light.
• Only massless particles, such as the photons which constitute light, are capable of traveling at the speed of light ie approximately 3 lac km/sec.
• Any material item cannot be accelerated to the speed of light because for doing so we would require an unlimited amount of energy.
• The theory states that as matter approaches the speed of light, the matter's mass becomes infinite.
• It was introduced in Einstein's 1905 paper "On the Electrodynamics of Moving Bodies".
• It is based on two postulates which are contradictory to classical mechanics
  • The laws of physics are the same for all observers in any inertial frame of reference relative to one another (principle of relativity).
  • The speed of light in a vacuum is the same for all observers, regardless of their relative motion or of the motion of the light source.

Important Points

• The theory has many surprising results which led to other observations. Some of these are:
  • Relativity of simultaneity: Two events, simultaneous for one observer, may not be simultaneous for another observer if the observers are in relative motion.
  • Time dilation: Moving clocks are measured to tick more slowly than an observer's "stationary" clock.
  • Length contraction: Objects are measured to be shortened in the direction that they are moving with respect to the observer.
  • Maximum speed is finite: No physical object, message or field line can travel faster than the speed of light in a vacuum.
  • The effect of gravity can only travel through space at the speed of light, not faster or instantaneously.
  • Mass–energy equivalence: E = mc2, energy and mass are equivalent and transmutable.

 Additional Information

• Daltons Law
  • ​The total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual component gases.
  • P_total = P_a+P_b+P_c.......................so on.
• Corpuscular theory of light
  • ​In optics, the corpuscular theory of light, arguably set forward by Descartes in 1637.
  • It states that light is made up of small discrete particles called "corpuscles" (little particles) which travel in a straight line with a finite velocity and possess impetus.
• Henry Law
  • The weight of a gas dissolved by a liquid is proportional to the pressure of the gas upon the liquid.
  • Holds only for dilute solutions and low gas pressures.

Concept:

• Momentum: The product of mass and velocity is called momentum or linear momentum.
  • It is denoted by P and unit is kg⋅ m/s
  • Momentum (P) = Mass (m) × velocity (V)
• Conservation of linear momentum: When there is no net external force on a system, then the total linear momentum of the system remains constant. This is called the conservation of linear momentum.

Explanation:

In the case of a rocket, we will take the rocket and its fuel as a system. There is no net force on this system, so the total momentum will be conserved.

• Thus the rockets work on the law of conservation of linear momentum is correct.
• The increased forward momentum of the rocket is equal but opposite in sign to the momentum of the ejected exhaust gases.

• The Law of definite proportions states that a compound will always contain the same proportion of elements by mass.
• It was given by Proust.
• Lavoisier discovered the role of oxygen in combustion.
• Democritus was a Greek Mathematician.
• Dalton gave the atomic theory which states that the atom of different size varies in size and mass.