Top 30 Physics MCQs for Competitive exams

பல்வேறு போட்டித் தேர்வுகளில் இயற்பியல் முக்கியப் பங்காற்றுகிறது, விண்ணப்பதாரர்களுக்கு அவர்களின் தயாரிப்பில் உதவ, நாங்கள் 30 கேள்விகளை (MCQs) தொகுத்துள்ளோம். உங்கள் இயற்பியல் அறிவை மேம்படுத்துவதற்கும், வரவிருக்கும் தேர்வுகளுக்கு உங்களை சிறப்பாக தயார்படுத்துவதற்கும் ஒவ்வொரு கேள்விக்கும் சரியான பதில் உள்ளது.

Top 30 Physics MCQs

Q1.What is the right-hand rule for magnetic fields?

(a) A rule that determines the direction of a magnetic field based on the direction of the current and the position of the observer’s thumb.

(b) A rule that determines the direction of a magnetic field based on the direction of the current and the position of the observer’s index finger.

(c) A rule that determines the direction of a magnetic field based on the direction of the current and the position of the observer’s middle finger.

(d) A rule that determines the direction of a magnetic field based on the position of the observer’s hand relative to the direction of the magnetic field.

Q2. What is the magnetic field strength at the center of a circular loop of wire carrying current?

(a) Zero

(b) Maximum

(d) One-third the maximum

Q3.What is the relationship between the magnetic field strength and the distance from a long, straight wire carrying current?

(a) Magnetic field strength increases with distance

(b) Magnetic field strength decreases with distance

(d) Magnetic field strength varies randomly with distance

Q4.Which type of magnetic material becomes magnetized in the presence of an external magnetic field?

(a) Diamagnetic material

(b) Paramagnetic material

(d) Non-magnetic material

Q5. What is the force experienced by a charged particle moving through a magnetic field?

(a) Electrical force

(b) Gravitational force

(d) Nuclear force

Q6.Which type of magnet is used in MRI machines?

(a) Permanent magnet

(b) Electromagnet

(d) Diamagnet

Q7.What is the difference between a uniform magnetic field and a non-uniform magnetic field?

(a) A uniform magnetic field has a constant magnitude and direction, while a non-uniform magnetic field varies in magnitude and direction.

(b) A uniform magnetic field varies in magnitude and direction, while a non-uniform magnetic field has a constant magnitude and direction.

(c) A uniform magnetic field is produced by a single magnet, while a non-uniform magnetic field is produced by multiple magnets.

(d) There is no difference between a uniform magnetic field and a non-uniform magnetic field.

Q8.What is the difference between a permanent magnet and an electromagnet?

(a) A permanent magnet is always magnetic, while an electromagnet can be turned on and off.

(b) A permanent magnet is made of iron, while an electromagnet is made of copper.

(d) A permanent magnet is used to generate electricity, while an electromagnet is used to attract ferromagnetic materials.

Q9.What is the relationship between electricity and magnetism?

(a) They are completely unrelated phenomena.

(b) They are independent phenomena that can occur separately.

(d) They are both caused by a strong nuclear force.

Q10.What is the unit of measurement for magnetic field strength?

(a) Tesla

(b) Joule

(d) Watt

Q11. Find the kinetic energy (in J) possessed by a body of mass 10 kg moving with a velocity of 5 m/s.

(a) 25

(b) 125

(d) 50

Q12.Find the potential energy gained by a body of mass 50 kg, if it is raised by 10m. (use g = 10 m/s2)

(a) 50

(b) 5000

(d) 25

Q13.During the free fall of the object, the decrease in potential energy, at any point in its path, appears as an equal amount of increase in ____________.

(a) Kinetic energy

(b) Work done

(d) Gravitational force

Q14. As an object falls freely its _______________.

(a) Kinetic energy gets converted into potential energy

(b) Potential energy gets converted into kinetic energy

(d) Gravitational force gets converted into momentum

Q15. Which among the following in false about work?

(a) If displacement is zero, work is zero

(b) Work done can be negative

(d) Its unit is Joule

Q16.Which law of physics relates Kinetic Energy to mass and velocity?

(a) Newton’s First Law

(b) Newton’s Second Law

(d) None of the above

Q17.Which type of energy is converted to Kinetic Energy when an object falls?

(a) Thermal Energy

(b) Potential Energy

(d) Nuclear Energy

Q18.What is the power of an engine that does 500 J of work in 2 seconds?

(a) 100 W

(b) 250 W

(d) 1000 W

Q19.Which of the following factors affects the amount of work done?

(a) Force applied

(b) Distance travelled

(d) All of the above

Q20.Which of the following is an example of negative work?

(a) Lifting a box

(b) Pulling a wagon

(d) Pushing a cart

Q21.The SI unit of acceleration is __________.

(a) ms-1

(b) ms-2

(d) m/s

Q22.1 joule is equal to 1 ____________.

(a) Nm

(b) N/m

(d) N/m²

Q23. 1 Pascal equals 1 ________________.

(a) Nm2

(b) Nm-2

(d) Nm-1

Q24.1 kWh = __________ × 106 J.

(a) 36

(b) 3.6

(d) 64

Q25.If a physical quantity has the units ampere per meter squared, what are it’s dimensions?

(a) [AL-2]

(b) [I M-2]

(d) [AM-2]

Q26. The unit of which physical quantity is not Pascal?

(a) Moment of inertia

(b) Pressure

(d) Young’s modulus

Q27.The SI unit of electric charge is –

(a) Ampere

(b) Coulomb

(d) Kelvin

Q28. “Curie” is the unit of –

(a) Radioactivity

(b) Temperature

(d) Energy

Q29. Which one of the following SI unit is not correctly matched?

(a) Work-Joule

(b) Force-Newton

(d) Pressure-Dyne

Q30. Which one of the following is not correctly matched?

(a) Knot – Unit to Measure speed of ship

(b) Nautical mile – Unit of distance used in navigation

(d) Light year – Unit of measuring time

Solution:

S1.Ans(b)

Sol. A rule that determines the direction of a magnetic field based on the direction of the current and the position of the observer’s index finger.

The right-hand rule for magnetic fields is a way to determine the direction of a magnetic field based on the direction of the current in a wire and the position of the observer’s hand. To use the rule, point your right hand in the direction of the current, curl your fingers in the direction of the magnetic field, and your thumb will point in the direction of the force experienced by a charged particle moving in that field.

S2.Ans(b)

Sol. The magnetic field strength at the center of a circular loop of wire carrying current is maximum. This occurs because the magnetic fields produced by the individual segments of the wire add together at the center of the loop.

S3.Ans(b)

Sol. The magnetic field strength produced by a long, straight wire carrying current decreases with distance from the wire. This is because the magnetic field lines spread out as they get farther from the wire, leading to a decrease in field strength.

S4.Ans(b)

Sol. Paramagnetic materials are materials that become weakly magnetized in the presence of an external magnetic field. This occurs because the external field aligns the magnetic moments of the atoms within the material.

S5.Ans(c)

Sol. A charged particle moving through a magnetic field experiences a magnetic force, which is perpendicular to both the velocity of the particle and the direction of the magnetic field. The magnitude of the force is proportional to the charge of the particle, the velocity of the particle, and the strength of the magnetic field.

Important Points:

Electrical force is the force of attraction or repulsion between charged particles. This force is responsible for the behavior of electrons in atoms, the interaction between charged particles in electric circuits, and the behavior of lightning and other electrical phenomena.
Gravitational force is the force of attraction between any two objects in the universe that have mass. This force is responsible for the behavior of planets in their orbits, the motion of objects on Earth, and the structure and evolution of the universe.
Nuclear force is the force that binds particles together in the nucleus of an atom. This force is responsible for the stability of the nucleus, the behavior of radioactive isotopes, and the energy production in stars and other astronomical objects.

S6.Ans(b)

Sol. MRI machines use strong magnetic fields to produce images of the body’s internal structures. These magnetic fields are produced by electromagnets, which are coils of wire with a current running through them that produce a magnetic field when energized.

S7.Ans(a)

Sol. A uniform magnetic field has a constant magnitude and direction, while a non-uniform magnetic field varies in magnitude and direction.

A uniform magnetic field is one in which the magnitude and direction of the magnetic field are constant throughout a given region. In contrast, a non-uniform magnetic field is one in which the magnitude and direction of the magnetic field vary from one point to another.

S8.Ans(a)

Sol. A permanent magnet is always magnetic, while an electromagnet can be turned on and off.

A permanent magnet is made of ferromagnetic material and always has a magnetic field. An electromagnet is made by wrapping a wire around a ferromagnetic core and passing a current through the wire. The magnetic field is created by the current flow and can be turned on and off by controlling the current flow.

S9.Ans(c)They are two aspects of the same fundamental force.

Electromagnetism is the interaction between electrically charged particles and magnetic fields. Moving electric charges create magnetic fields, and changing magnetic fields create electric fields. This mutual relationship is described by Maxwell’s equations, which unify the phenomena of electricity and magnetism and explain the behavior of electromagnetic waves, such as light.
The study of electromagnetism is crucial to understanding many phenomena in the natural world, such as the behavior of electrons in atoms, the functioning of electric motors, and the propagation of radio waves.

S10.Ans(a)

Sol. The unit of measurement for magnetic field strength is the tesla (T), which is equivalent to 1 weber per square meter. Another commonly used unit is the gauss (G), with 1 T = 10,000 G.

Important Points:

Joule (symbol: J) is the unit of measurement for energy or work, which is defined as the amount of work done when a force of one newton is applied over a distance of one meter.
Ohm (symbol: Ω) is the unit of measurement for electrical resistance, which is the opposition of a material or a circuit to the flow of electric current.
Watt (symbol: W) is the unit of measurement for power, which is the rate at which work is done or energy is transferred. One watt is equivalent to one joule per second.

S11. Ans.(b)

Sol.

The kinetic energy (KE) of an object is given by the formula:

KE = 1/2 x m x v2

Where m is the mass of the object and v is its velocity.
Using this formula and the values given in the question, we can calculate the kinetic energy as:

KE = 1/2 * 10 kg * (5 m/s)2

KE = 125 J

Therefore, the kinetic energy possessed by a body of mass 10 kg moving with a velocity of 5 m/s is 125 Joules.

S12.Ans.(b)

Sol.

The potential energy (PE) gained by a body when it is raised to a certain height above the ground is given by the formula:

PE = m * g * h

Where m is the mass of the object, g is the acceleration due to gravity, and h is the height to which the object is raised.
Using this formula and the values given in the question, we can calculate the potential energy gained as:

PE = 50 kg * 10 m/s2 * 10 m

PE = 5000 J

Therefore, the potential energy gained by a body of mass 50 kg when it is raised by 10m is 5000 Joules.

S13. Ans.(a)

Sol. The correct answer is (a) Kinetic energy.

During the free fall of an object, the object loses potential energy due to the force of gravity, but gains an equal amount of kinetic energy as it gains speed. This is because the potential energy is converted to kinetic energy as the object falls. Therefore, as the potential energy decreases, the kinetic energy of the object increases proportionally.
The work done by the force of gravity on the object is also equal to the increase in kinetic energy, according to the work-energy theorem. However, this work is not stored as energy, but rather used to increase the object’s velocity.
Heat energy is not relevant in this scenario because there is no friction or other factors that would cause energy to be converted to heat.

S14.Ans.(b)

Sol. Before the object begins falling, it has gravitational potential energy which can be calculated by mgh, So the initial potential energy will equal the kinetic energy of the object right before it hits the ground. The potential energy has been converted into kinetic energy.

S15. Ans.(c)

Sol. Whenever a force is applied to an object, causing the object to move, work is done by the force. Work done due to displacement caused by a force is a scalar quantity. Work can be either positive or negative.The unit of work is the unit of energy, the joule (J). 1 J = 1 N m.

S16.Ans(b)

Sol. According to Newton’s Second Law, Kinetic Energy is directly proportional to the mass of an object and the square of its velocity.

S17.Ans(b)

Sol. The correct answer is (b) Potential Energy.

When an object falls, the potential energy it had due to its position above the ground or other surface is converted into kinetic energy. This happens because the object’s potential energy decreases as it moves closer to the ground, and this decrease is accompanied by an increase in kinetic energy.

S18.Ans(b)

Sol.The correct answer is (b) 250W.

Power is defined as the rate at which work is done, or the amount of energy transferred per unit time. The formula for power is:

Power = Work / Time

In this case, the engine does 500 J of work in 2 seconds. So, the power of the engine is:

Power = Work / Time = 500 J / 2 s = 250 W

Therefore, the power of the engine is 250 W.

S19.Ans(d)

Sol. The correct answer is (d) All of the above.

The amount of work done on an object is defined as the product of the force applied to the object and the distance over which the force is applied. Therefore, both the force applied and the distance traveled affect the amount of work done.
Moreover, the angle between the force and the displacement also affects the amount of work done. When the force is applied in the same direction as the displacement, the work done is maximum. However, when the force is applied perpendicular to the displacement, the work done is zero.
Therefore, all the factors – force applied, distance travelled, and angle between force and displacement – affect the amount of work done.

S20.Ans(c)

Sol. Slowing down a car. Negative work is done when the force applied is in the opposite direction to the displacement of the object. Slowing down a car requires a force opposite to its direction of motion, hence negative work is done.

S21. Ans.(b)

Sol. The SI unit for acceleration is metre per second squared (ms−2).

The SI unit of acceleration is meters per second squared (ms-2). Acceleration is defined as the rate of change of velocity per unit time. It measures how quickly the velocity of an object changes over time. The unit “ms-2” represents meters per second squared, indicating that the velocity changes by a certain number of meters per second per second.

S22. Ans.(a)

Sol. 1 joule is equal to 1 Nm.

Joule (J) is the unit of energy or work in the International System of Units (SI). It is defined as the amount of work done when a force of 1 Newton (N) is applied over a distance of 1 meter (m). Therefore, 1 joule is equal to 1 Newton-meter (Nm).

S23.Ans.(b)

Sol. The correct answer is (b) Nm-2.

Pascal (Pa) is the unit of pressure in the International System of Units (SI). It is defined as the pressure exerted by a force of 1 Newton (N) uniformly distributed over an area of 1 square meter (m2). Therefore, 1 Pascal is equal to 1 Newton per square meter (Nm-2), indicating the pressure exerted by a force of 1 Newton distributed over an area of 1 square meter.

S24.Ans.(b)

Sol. The correct answer is (b) 3.6.

1 kWh (kilowatt-hour) is equal to 3.6 × 106 joules (J).

The kilowatt-hour (kWh) is a unit of energy commonly used for measuring electrical energy consumption. It represents the energy consumed when a power of 1 kilowatt (kW) is used for 1 hour. To convert kWh to joules, we multiply by the conversion factor of 3.6 × 106.

S25. Ans.(c)

Sol. If a physical quantity has the units ampere per meter squared, then it’s dimensions are I L-2.

S26. Ans.(a)

Sol. The correct answer is (a) Moment of inertia.

The unit of moment of inertia is not Pascal. Moment of inertia is a property related to the distribution of mass in a rotating body and is expressed in units such as kilogram-meter squared (kg·m2) in the SI system. It is not directly related to pressure, stress, or Young’s modulus, which are all measured in Pascal (Pa) or derived from Pascal.

S27. Ans.(b)

Sol. The correct answer is (b) Coulomb.

The SI unit of electric charge is the Coulomb (C). The Coulomb is defined as the amount of electric charge carried by a current of 1 Ampere (A) flowing for 1 second. It is the fundamental unit of electric charge in the International System of Units (SI). The other options, Ampere (A), Esu, and Kelvin, are not the SI units of electric charge. Ampere is the SI unit of electric current, Esu (Electrostatic Unit) is a CGS unit of electric charge, and Kelvin is the SI unit of temperature.

S28. Ans.(a)

Sol. The correct answer is (a) Radioactivity.

Curie (Ci) is the unit of radioactivity. It is named after Marie Curie, a pioneering physicist and chemist who conducted groundbreaking research on radioactivity. The Curie is a unit of activity that measures the rate at which a radioactive substance undergoes decay or disintegration. It is equal to 3.7 × 1010 disintegrations per second, which is approximately the activity of one gram of radium-226. The other options, temperature, heat, and energy, are not measured in Curie.

S29. Ans. (d)

Sol. Pascal is the unit of pressure in the international system of Units (SI). Dyne is unit of force in CGS system. Clearly, option (d) is not correctly paired.

S30. Ans.(d)

Sol. The correct answer is (d) Light year – Unit of measuring time.

Light-year is not a unit of measuring time; it is a unit of measuring astronomical distances. A light year is the distance that light travels in one year in a vacuum. It is commonly used in astronomy to represent vast distances between celestial objects. The other options are correctly matched:
Knot – Unit to Measure speed of ship: A knot is a unit of speed used in navigation and maritime contexts. It represents one nautical mile per hour.
Nautical mile – Unit of distance used in navigation: A nautical mile is a unit of distance used primarily in maritime and aviation navigation. It is defined as one minute of latitude along any meridian.
Angstrom – Unit of length: The angstrom (symbol: Å) is a unit of length commonly used to measure atomic and molecular scales. It is equal to 0.1 nanometers or 10-10 meters.

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