Assertion Reason Questions with Answers | Class 12 physics Important Practice for Board Exams
Chapter: Electric Charges and Fields
Q1.
Assertion (A): Like charges repel and unlike charges attract.
Reason (R): The electrostatic force between two point charges is inversely proportional to the square of the distance between them.
✅ Answer: A is true, R is true, and R is the correct explanation of A.
Q2.
Assertion (A): The electrostatic force is a conservative force.
Reason (R): Work done in moving a charge between two points is path-independent.
✅ Answer: A is true, R is true, and R is the correct explanation of A.
Q3.
Assertion (A): Coulomb’s law constant k depends on the medium between charges.
Reason (R): The relative permittivity of medium modifies the effective force between charges.
✅ Answer: A is true, R is true, and R is the correct explanation of A.
Q4.
Assertion (A): The electric field inside a uniformly charged spherical shell is zero.
Reason (R): Net flux through a Gaussian surface inside the shell is zero.
✅ Answer: A is true, R is true, and R is the correct explanation of A.
Q5.
Assertion (A): Electric field is always normal to the surface of a conductor in electrostatic equilibrium.
Reason (R): If tangential components exist, charges will move and equilibrium cannot be maintained.
✅ Answer: A is true, R is true, and R is the correct explanation of A.
Q6.
Assertion (A): Gauss’s law is valid only for spherically symmetric charge distribution.
Reason (R): Gauss’s law is derived from Coulomb’s law assuming spherical charges.
✅ Answer: A is false, R is false.
Q7.
Assertion (A): The electric field due to a dipole falls off faster than that due to a point charge.
Reason (R): For large distance, field of dipole ∝ 1/r3 while for point charge ∝ 1/r2.
✅ Answer: A is true, R is true, and R is the correct explanation of A.
Q8.
Assertion (A): Net electric flux through a closed surface depends on the charge enclosed, not on external charges.
Reason (R): According to Gauss’s theorem, external charges do not contribute to net flux.
✅ Answer: A is true, R is true, and R is the correct explanation of A.
Q9.
Assertion (A): The total charge of an isolated system is conserved.
Reason (R): Electric charge can neither be created nor destroyed.
✅ Answer: A is true, R is true, and R is the correct explanation of A.
Q10.
Assertion (A): The electric field inside a conductor is zero in electrostatic equilibrium.
Reason (R): Free charges in the conductor move to cancel any internal field.
✅ Answer: A is true, R is true, and R is the correct explanation of A.
Q11.
Assertion (A): Charge is always conserved.
Reason (R): It can neither be created nor destroyed.
✅ Answer: A is true, R is true, and R explains A.
Q12.
Assertion (A): Coulomb’s law is valid only for stationary charges.
Reason (R): Moving charges produce both electric and magnetic fields.
✅ Answer: A is true, R is true, and R explains A.
Q13.
Assertion (A): Force between two charges is equal and opposite.
Reason (R): Electrostatic force obeys Newton’s third law.
✅ Answer: A is true, R is true, and R explains A.
Q14.
Assertion (A): Field lines start from positive charges and end at negative charges.
Reason (R): They show the direction of force on a positive test charge.
✅ Answer: A is true, R is true, and R explains A.
Q15.
Assertion (A): Electric flux is scalar.
Reason (R): It is the dot product of field vector and area vector.
✅ Answer: A is true, R is true, and R explains A.
Q16.
Assertion (A): In electrostatic shielding, field inside a cavity is zero.
Reason (R): Charges reside only on the outer surface of a conductor.
✅ Answer: A is true, R is true, and R explains A.
Q17.
Assertion (A): Force between charges is unaffected by presence of other charges.
Reason (R): Superposition principle applies to electrostatic forces.
✅ Answer: A is true, R is true, and R explains A.
Q18.
Assertion (A): Gauss’s law is most useful for symmetric charge distributions.
Reason (R): In such cases, the electric field can be taken outside the integral.
✅ Answer: A is true, R is true, and R explains A.
Q19.
Assertion (A): Inside a hollow conductor, the electric field is zero.
Reason (R): All charges reside on the outer surface in equilibrium.
✅ Answer: A is true, R is true, and R explains A.
Q20.
Assertion (A): Electrostatic force acts along the line joining charges.
Reason (R): It is a central force.
✅ Answer: A is true, R is true, and R explains A.
Q21.
Assertion (A): Like charges repel and unlike charges attract.
Reason (R): The electrostatic force is inversely proportional to the square of the distance between two charges.
✅ Answer: A is true, R is true, and R correctly explains A.
Q22.
Assertion (A): Coulomb’s law constant kkk depends on the medium.
Reason (R): The relative permittivity (εrε_rεr) of the medium modifies the force between charges.
✅ Answer: A is true, R is true, and R correctly explains A.
Q23.
Assertion (A): The electrostatic force is a conservative force.
Reason (R): Work done in moving a charge is path-independent.
✅ Answer: A is true, R is true, and R correctly explains A.
Q24.
Assertion (A): The electric field inside a uniformly charged spherical shell is zero.
Reason (R): Net flux through a Gaussian surface inside the shell is zero.
✅ Answer: A is true, R is true, and R correctly explains A.
Q25.
Assertion (A): Electric field is always perpendicular to the surface of a conductor in electrostatic equilibrium.
Reason (R): Tangential components of the field would cause charge motion and disturb equilibrium.
✅ Answer: A is true, R is true, and R correctly explains A.
Q26.
Assertion (A): The electric field due to a dipole decreases faster with distance compared to that of a point charge.
Reason (R): At large distances, dipole field ∝ 1/r31/r^31/r3 while point charge field ∝ 1/r21/r^21/r2.
✅ Answer: A is true, R is true, and R correctly explains A.
Q27.
Assertion (A): Gauss’s law can be applied to any closed surface.
Reason (R): It is independent of the shape or size of the Gaussian surface.
✅ Answer: A is true, R is true, and R correctly explains A.
Q28.
Assertion (A): Electric flux through a closed surface depends only on enclosed charge.
Reason (R): External charges do not contribute to net flux, as per Gauss’s law.
✅ Answer: A is true, R is true, and R correctly explains A.
Q29.
Assertion (A): The electric field is zero inside a conductor in electrostatic equilibrium.
Reason (R): Free charges move within the conductor to cancel any internal field.
✅ Answer: A is true, R is true, and R correctly explains A.
Q30.
Assertion (A): The electric field lines never cross each other.
Reason (R): If they did, the field at the intersection would have two directions, which is impossible.
✅ Answer: A is true, R is true, and R correctly explains A.
Q31.
Assertion (A): The total charge of an isolated system is conserved.
Reason (R): Charge can neither be created nor destroyed.
✅ Answer: A is true, R is true, and R correctly explains A.
Q32.
Assertion (A): Coulomb’s law is valid only for stationary point charges.
Reason (R): Moving charges produce magnetic as well as electric fields.
✅ Answer: A is true, R is true, and R correctly explains A.
Q33.
Assertion (A): The force between two charges is equal and opposite.
Reason (R): Electrostatic force obeys Newton’s third law.
✅ Answer: A is true, R is true, and R correctly explains A.
Q34.
Assertion (A): Electric field lines are always directed away from positive charge.
Reason (R): Field lines indicate the direction of force on a positive test charge.
✅ Answer: A is true, R is true, and R correctly explains A.
Q35.
Assertion (A): Electric flux is a scalar quantity.
Reason (R): It is the dot product of electric field and area vector.
✅ Answer: A is true, R is true, and R correctly explains A.
Q36.
Assertion (A): In electrostatic shielding, the electric field inside a conductor cavity is zero.
Reason (R): The charges reside only on the outer surface of a conductor.
✅ Answer: A is true, R is true, and R correctly explains A.
Q37.
Assertion (A): The force between two charges is independent of the presence of other charges.
Reason (R): Electrostatic forces obey the principle of superposition.
✅ Answer: A is true, R is true, and R correctly explains A.
Q38.
Assertion (A): Gauss’s law can be used to calculate electric field in highly symmetric charge distributions.
Reason (R): In such cases, the electric field can be easily taken out of the flux integral.
✅ Answer: A is true, R is true, and R correctly explains A.
Q39.
Assertion (A): Electric field inside a hollow charged conductor is zero.
Reason (R): All charges reside on the outer surface in electrostatic equilibrium.
✅ Answer: A is true, R is true, and R correctly explains A.
Q40.
Assertion (A): Electrostatic force acts along the line joining two charges.
Reason (R): Electrostatic force is a central force.
✅ Answer: A is true, R is true, and R correctly explains A.
Q41.
Assertion (A): Like charges repel and unlike charges attract.
Reason (R): The electrostatic force between two point charges varies as 1/r2
✅ Answer: A is true, R is true, and R explains A.
Q42.
Assertion (A): Coulomb’s constant depends on the medium.
Reason (R): Electrostatic force decreases in a medium with higher permittivity.
✅ Answer: A is true, R is true, and R explains A.
Q43.
Assertion (A): Electrostatic force is conservative.
Reason (R): Work done depends only on initial and final positions.
✅ Answer: A is true, R is true, and R explains A.
Q44.
Assertion (A): The electric field inside a uniformly charged spherical shell is zero.
Reason (R): Net flux through a Gaussian surface inside is zero.
✅ Answer: A is true, R is true, and R explains A.
Q45.
Assertion (A): In electrostatic equilibrium, the electric field is normal to the conductor surface.
Reason (R): Tangential field components would move charges.
✅ Answer: A is true, R is true, and R explains A.
Q46.
Assertion (A): Dipole field decreases faster with distance than that of a point charge.
Reason (R): Dipole field ∝ 1/r3whereas point charge field ∝ 1/r2
✅ Answer: A is true, R is true, and R explains A.
Q47.
Assertion (A): Gauss’s law can be applied to any closed surface.
Reason (R): It holds regardless of the shape or size of the surface.
✅ Answer: A is true, R is true, and R explains A.
Q48.
Assertion (A): Electric flux depends only on enclosed charge.
Reason (R): External charges do not contribute to net flux.
✅ Answer: A is true, R is true, and R explains A.
Q49.
Assertion (A): Electric field inside a conductor is zero in equilibrium.
Reason (R): Charges redistribute to cancel any internal field.
✅ Answer: A is true, R is true, and R explains A.
Q50.
Assertion (A): Electric field lines never intersect.
Reason (R): At any point, field has a unique direction.
✅ Answer: A is true, R is true, and R explains A.
Assertion Reason Questions with Answers | Class 12 physics Important Practice for Board Exams
Chapter: Electric Potential and Capacitance
Q1.
Assertion (A): Electric potential at a point is the work done per unit charge in bringing a test charge from infinity to that point.
Reason (R): Potential is a scalar quantity.
✅ Answer: A is true, R is true, and R correctly explains A.
Q2.
Assertion (A): The potential difference between two points is path-independent.
Reason (R): Electrostatic field is conservative.
✅ Answer: A is true, R is true, and R correctly explains A.
Q3.
Assertion (A): Electric potential due to a point charge decreases as distance increases.
Reason (R): V=kQ/r
✅ Answer: A is true, R is true, and R correctly explains A.
Q4.
Assertion (A): Potential inside a uniformly charged spherical shell is constant.
Reason (R): Electric field inside the shell is zero.
✅ Answer: A is true, R is true, and R correctly explains A.
Q5.
Assertion (A): Potential at the center of a uniformly charged ring is finite.
Reason (R): The potential is the algebraic sum of contributions from all elements of the ring.
✅ Answer: A is true, R is true, and R correctly explains A.
Q6.
Assertion (A): Work done in moving a charge around a closed loop in an electrostatic field is zero.
Reason (R): Electrostatic field is conservative.
✅ Answer: A is true, R is true, and R correctly explains A.
Q7.
Assertion (A): Equipotential surfaces are always perpendicular to electric field lines.
Reason (R): Work done in moving a charge on an equipotential surface is zero.
✅ Answer: A is true, R is true, and R correctly explains A.
Q8.
Assertion (A): Potential at a point due to an electric dipole is zero on its equatorial line.
Reason (R): Contributions from the two charges cancel each other on the equatorial line.
✅ Answer: A is true, R is true, and R correctly explains A.
Q9.
Assertion (A): Potential is continuous across a charged surface.
Reason (R): Electric field is the gradient of potential.
✅ Answer: A is true, R is true, and R correctly explains A.
Q10.
Assertion (A): The capacitance of an isolated spherical conductor depends only on its radius.
Reason (R): Capacitance is given by C=4πε0R
✅ Answer: A is true, R is true, and R correctly explains A.
Q11.
Assertion (A): The capacitance of a parallel plate capacitor is directly proportional to plate area and inversely proportional to separation.
Reason (R): C=ε0A.
✅ Answer: A is true, R is true, and R correctly explains A.
Q12.
Assertion (A): Adding a dielectric increases the capacitance of a capacitor.
Reason (R): The electric field inside the dielectric decreases.
✅ Answer: A is true, R is true, and R correctly explains A.
Q13.
Assertion (A): The energy stored in a capacitor is 1/2CV2
Reason (R): Work done in charging the capacitor is stored as electrostatic energy.
✅ Answer: A is true, R is true, and R correctly explains A.
Q14.
Assertion (A): Potential difference across capacitors connected in parallel is the same.
Reason (R): All capacitors are connected directly across the supply voltage.
✅ Answer: A is true, R is true, and R correctly explains A.
Q15.
Assertion (A): In series combination of capacitors, charge on each capacitor is the same.
Reason (R): Equivalent charge flows through the same series path.
✅ Answer: A is true, R is true, and R correctly explains A.
Q16.
Assertion (A): The capacitance of a capacitor does not depend on the charge stored.
Reason (R): Capacitance depends only on geometry and dielectric medium.
✅ Answer: A is true, R is true, and R correctly explains A.
Q17.
Assertion (A): The potential of the earth is taken as zero.
Reason (R): The earth can absorb or supply unlimited charge without changing its potential.
✅ Answer: A is true, R is true, and R correctly explains A.
Q18.
Assertion (A): The potential at infinity due to any finite system of charges is zero.
Reason (R): Distance from charges at infinity becomes infinite, making potential vanish.
✅ Answer: A is true, R is true, and R correctly explains A.
Q19.
Assertion (A): In a capacitor partially filled with dielectric, the effective capacitance lies between values with and without dielectric.
Reason (R): Effective dielectric constant lies between 1 and εr\varepsilon_rεr.
✅ Answer: A is true, R is true, and R correctly explains A.
Q20.
Assertion (A): Energy stored in a capacitor is inversely proportional to plate separation for constant charge.
Reason (R): For constant Q, U=Q2/2C and C∝1/d1.
✅ Answer: A is true, R is true, and R correctly explains A.
Q21.
Assertion (A): The potential due to an electric dipole is zero at all points on its equatorial line.
Reason (R): Electric field due to a dipole is also zero on the equatorial line.
✅ Answer: A is true, R is false.
Q22.
Assertion (A): Work done in carrying a charge between two points on an equipotential surface is zero.
Reason (R): Electric field is tangential to the equipotential surface.
✅ Answer: A is true, R is false.
Q23.
Assertion (A): Potential at the center of a uniformly charged spherical shell is constant.
Reason (R): Electric field inside the shell is zero everywhere.
✅ Answer: A is true, R is true, and R correctly explains A.
Q24.
Assertion (A): The potential difference between two points in an electric field is equal to the negative line integral of field.
Reason (R): Potential decreases in the direction of the field.
✅ Answer: A is true, R is true, and R correctly explains A.
Q25.
Assertion (A): A capacitor stores energy in its plates.
Reason (R): The potential energy of a capacitor exists in the electric field between the plates.
✅ Answer: A is true, R is false.
Q26.
Assertion (A): The capacitance of a parallel plate capacitor increases if dielectric slab thickness increases (keeping other factors constant).
Reason (R): Dielectric reduces the effective electric field inside the capacitor.
✅ Answer: A is false, R is true.
Q27.
Assertion (A): The capacitance of a capacitor is independent of the potential difference applied across it.
Reason (R): Capacitance depends only on geometry and dielectric medium.
✅ Answer: A is true, R is true, and R correctly explains A.
Q28.
Assertion (A): If two identical capacitors are connected in parallel, their equivalent capacitance is less than that of a single capacitor.
Reason (R): In parallel connection, potential difference across each capacitor is the same.
✅ Answer: A is false, R is true.
Q29.
Assertion (A): A dielectric always increases the capacitance of a capacitor.
Reason (R): Dielectric reduces the potential difference for a given charge.
✅ Answer: A is true, R is true, and R correctly explains A.
Q30.
Assertion (A): The electric potential at infinity is taken as zero.
Reason (R): At infinite distance, the effect of a finite charge distribution vanishes.
✅ Answer: A is true, R is true, and R correctly explains A.
Q31.
Assertion (A): In a series combination of capacitors, the reciprocal of the equivalent capacitance is the sum of reciprocals of individual capacitances.
Reason (R): In series, charge is the same across each capacitor.
✅ Answer: A is true, R is true, and R correctly explains A.
Q32.
Assertion (A): A capacitor with dielectric stores more energy than the same capacitor without dielectric when connected to the same battery.
Reason (R): Capacitance increases with dielectric.
✅ Answer: A is true, R is true, and R correctly explains A.
Q33.
Assertion (A): If plates of a charged capacitor are moved apart (battery disconnected), the potential difference decreases.
Reason (R): Capacitance decreases with increased separation.
✅ Answer: A is false, R is true.
Q34.
Assertion (A): Energy density in an electric field is given by 1/2εE2
Reason (R): Energy is stored per unit volume of the region occupied by the electric field.
✅ Answer: A is true, R is true, and R correctly explains A.
Q35.
Assertion (A): The work done to charge a capacitor is equal to the energy stored in it.
Reason (R): Work done in moving charge gets stored in the capacitor in the form of potential energy.
✅ Answer: A is true, R is true, and R correctly explains A.
Q36.
Assertion (A): Potential difference between two points depends only on electric field and not on the path taken.
Reason (R): Electrostatic field is non-conservative.
✅ Answer: A is true, R is false.
Q37.
Assertion (A): For a given separation and area, the capacitance of a capacitor decreases if a dielectric of lower dielectric constant is introduced.
Reason (R): Capacitance is directly proportional to dielectric constant.
✅ Answer: A is true, R is true, and R correctly explains A.
Q38.
Assertion (A): A parallel plate capacitor completely filled with dielectric has higher capacitance than when it is half-filled.
Reason (R): Effective capacitance in partial filling is equivalent to series and parallel combinations of dielectrics.
✅ Answer: A is true, R is true, and R correctly explains A.
Q39.
Assertion (A): Potential at any point between two oppositely charged parallel plates varies linearly with distance.
Reason (R): Electric field between parallel plates is uniform.
✅ Answer: A is true, R is true, and R correctly explains A.
Q40.
Assertion (A): The effective capacitance of two capacitors in parallel is greater than either of them.
Reason (R): In parallel, equivalent plate area increases.
✅ Answer: A is true, R is true, and R correctly explains A.
Assertion Reason Questions with Answers | Class 12 physics Important Practice for Board Exams
Chapter: Current Electricity
Q1.
Assertion (A): Drift velocity of electrons is directly proportional to current.
Reason (R): I=neAvdI = neAv_dI=neAvd.
✅ Answer: A is true, R is true, and R correctly explains A.
Q2.
Assertion (A): The average thermal speed of electrons is much greater than their drift speed.
Reason (R): Drift velocity is of the order of mm/s, while thermal velocity is about 10510^5105 m/s.
✅ Answer: A is true, R is true, and R correctly explains A.
Q3.
Assertion (A): Ohm’s law is a fundamental law of nature.
Reason (R): It is valid for all conducting materials.
✅ Answer: A is false, R is false.
Q4.
Assertion (A): Resistance of a metallic conductor increases with temperature.
Reason (R): Number density of free electrons increases with temperature.
✅ Answer: A is true, R is false.
Q5.
Assertion (A): The resistivity of a semiconductor decreases with increase in temperature.
Reason (R): Increase in temperature generates more charge carriers.
✅ Answer: A is true, R is true, and R correctly explains A.
Q6.
Assertion (A): The resistance of a wire is proportional to its length and inversely proportional to area of cross-section.
Reason (R): R=ρL/A
✅ Answer: A is true, R is true, and R correctly explains A.
Q7.
Assertion (A): In series combination of resistors, the current through each resistor is the same.
Reason (R): The same current flows through all components of a series circuit.
✅ Answer: A is true, R is true, and R correctly explains A.
Q8.
Assertion (A): In parallel combination of resistors, potential difference across each resistor is the same.
Reason (R): All resistors are connected directly across the same two points.
✅ Answer: A is true, R is true, and R correctly explains A.
Q9.
Assertion (A): Kirchhoff’s current law (KCL) is based on conservation of charge.
Reason (R): The algebraic sum of currents entering a junction equals zero.
✅ Answer: A is true, R is true, and R correctly explains A.
Q10.
Assertion (A): Kirchhoff’s voltage law (KVL) is based on conservation of energy.
Reason (R): The algebraic sum of potential differences in a closed loop is zero.
✅ Answer: A is true, R is true, and R correctly explains A.
Q11.
Assertion (A): Wheatstone bridge is most sensitive when all four resistances are of the same order.
Reason (R): Sensitivity increases when deflection in galvanometer is maximum for small changes.
✅ Answer: A is true, R is true, and R correctly explains A.
Q12.
Assertion (A): Potentiometer can measure emf more accurately than a voltmeter.
Reason (R): Potentiometer does not draw any current from the cell.
✅ Answer: A is true, R is true, and R correctly explains A.
Q13.
Assertion (A): Internal resistance of a cell decreases with increase in temperature.
Reason (R): Conductivity of electrolyte increases with temperature.
✅ Answer: A is true, R is true, and R correctly explains A.
Q14.
Assertion (A): In an ideal cell, terminal voltage is equal to emf.
Reason (R): In an ideal cell, internal resistance is zero.
✅ Answer: A is true, R is true, and R correctly explains A.
Q15.
Assertion (A): A galvanometer can be converted into an ammeter by connecting a high resistance in series.
Reason (R): Series resistance allows large current to pass through the galvanometer safely.
✅ Answer: A is false, R is false.
Q16.
Assertion (A): A galvanometer can be converted into a voltmeter by connecting a high resistance in series.
Reason (R): This ensures that only a small current passes through the galvanometer.
✅ Answer: A is true, R is true, and R correctly explains A.
Q17.
Assertion (A): Drift velocity of electrons in a conductor decreases if its cross-sectional area is increased (for same current).
Reason (R): vd=I/neA.
✅ Answer: A is true, R is true, and R correctly explains A.
Q18.
Assertion (A): Resistivity of a conductor is independent of its dimensions.
Reason (R): Resistivity depends only on the material of the conductor.
✅ Answer: A is true, R is true, and R correctly explains A.
Q19.
Assertion (A): In a balanced Wheatstone bridge, no current flows through the galvanometer.
Reason (R): Potential difference across galvanometer is zero.
✅ Answer: A is true, R is true, and R correctly explains A.
Q20.
Assertion (A): The heating effect of current is directly proportional to the square of current.
Reason (R): Heat produced in time t is given by H=I2Rt
✅ Answer: A is true, R is true, and R correctly explains A.
Kirchhoff’s Current Law (KCL)
Q21.
Assertion (A): Kirchhoff’s current law is based on conservation of charge.
Reason (R): The algebraic sum of currents at a junction is zero.
✅ Answer: A is true, R is true, and R correctly explains A.
Q22.
Assertion (A): In a circuit, current entering a junction is always equal to the current leaving it.
Reason (R): Charge cannot accumulate at a junction.
✅ Answer: A is true, R is true, and R correctly explains A.
Q23.
Assertion (A): KCL is valid for both steady current and alternating current circuits.
Reason (R): KCL is based on conservation of mass.
✅ Answer: A is true, R is false.
Q24.
Assertion (A): At a junction, sum of incoming currents may not equal sum of outgoing currents if the circuit contains a capacitor.
Reason (R): In case of charging capacitor, displacement current must also be considered.
✅ Answer: A is true, R is true, and R correctly explains A.
Q25.
Assertion (A): Kirchhoff’s current law can be derived from Gauss’s law.
Reason (R): Electric flux through a closed surface is proportional to enclosed charge.
✅ Answer: A is true, R is true, but R does not explain A.
Kirchhoff’s Voltage Law (KVL)
Q26.
Assertion (A): Kirchhoff’s voltage law is based on conservation of energy.
Reason (R): Algebraic sum of potential differences in a closed loop is zero.
✅ Answer: A is true, R is true, and R correctly explains A.
Q27.
Assertion (A): KVL is valid only in electrostatic fields.
Reason (R): In the presence of changing magnetic flux, induced emf violates KVL.
✅ Answer: A is true, R is true, and R correctly explains A.
Q28.
Assertion (A): KVL can be applied to measure emf of a cell.
Reason (R): Total energy gained by unit charge equals total energy lost.
✅ Answer: A is true, R is true, and R correctly explains A.
Q29.
Assertion (A): In a closed circuit loop, algebraic sum of currents is zero.
Reason (R): This follows from conservation of energy.
✅ Answer: A is false, R is false.
Q30.
Assertion (A): KVL is applicable to both AC and DC circuits.
Reason (R): It depends only on energy conservation, not on type of source.
✅ Answer: A is true, R is true, and R correctly explains A.
Application in Circuits
Q31.
Assertion (A): In Wheatstone bridge, balance condition is derived using Kirchhoff’s laws.
Reason (R): At balance, no current flows through the galvanometer.
✅ Answer: A is true, R is true, and R correctly explains A.
Q32.
Assertion (A): Kirchhoff’s laws can solve networks where Ohm’s law alone is insufficient.
Reason (R): They handle multiple sources and junctions simultaneously.
✅ Answer: A is true, R is true, and R correctly explains A.
Q33.
Assertion (A): In a circuit with two loops, KVL must be applied to each loop separately.
Reason (R): Each loop gives an independent equation.
✅ Answer: A is true, R is true, and R correctly explains A.
Q34.
Assertion (A): In complex circuits, number of independent equations from Kirchhoff’s laws equals number of unknowns.
Reason (R): Junction rule + loop rule form simultaneous equations.
✅ Answer: A is true, R is true, and R correctly explains A.
Q35.
Assertion (A): Superposition theorem is based on Kirchhoff’s laws.
Reason (R): Linear circuits can be analyzed by applying KCL and KVL to each source independently.
✅ Answer: A is true, R is true, and R correctly explains A.
Limitations
Q36.
Assertion (A): Kirchhoff’s laws are not applicable at very high frequencies.
Reason (R): At high frequencies, radiation effects and inductance cannot be neglected.
✅ Answer: A is true, R is true, and R correctly explains A.
Q37.
Assertion (A): KCL is invalid when displacement current is present.
Reason (R): Maxwell’s correction restores its validity.
✅ Answer: A is false, R is true.
Q38.
Assertion (A): KVL fails in presence of time-varying magnetic fields.
Reason (R): Faraday’s law induces emf, making algebraic sum of potential differences non-zero.
✅ Answer: A is true, R is true, and R correctly explains A.
Q39.
Assertion (A): Kirchhoff’s laws are only approximate, not exact.
Reason (R): Radiation losses and distributed parameters are ignored.
✅ Answer: A is true, R is true, and R correctly explains A.
Q40.
Assertion (A): KVL does not apply to superconductors.
Reason (R): In superconductors, resistance is zero.
✅ Answer: A is false, R is false.
Mixed Applications
Q41.
Assertion (A): The loop rule ensures charge conservation.
Reason (R): The sum of currents at a junction is zero.
✅ Answer: A is false, R is false.
Q42.
Assertion (A): In any closed loop, algebraic sum of IR drops equals algebraic sum of emfs.
Reason (R): Charges lose exactly the energy they gain while moving in a loop.
✅ Answer: A is true, R is true, and R correctly explains A.
Q43.
Assertion (A): A network with ‘n’ nodes has only (n–1) independent KCL equations.
Reason (R): One equation is redundant because of conservation law.
✅ Answer: A is true, R is true, and R correctly explains A.
Q44.
Assertion (A): In solving circuits, number of independent KVL equations equals number of independent loops.
Reason (R): Each loop gives a unique equation.
✅ Answer: A is true, R is true, and R correctly explains A.
Q45.
Assertion (A): Kirchhoff’s laws are valid only for lumped parameter circuits.
Reason (R): They assume negligible field energy storage between elements.
✅ Answer: A is true, R is true, and R correctly explains A.
Conceptual
Q46.
Assertion (A): KCL requires instantaneous currents to be considered in AC circuits.
Reason (R): Phasor addition is used instead of algebraic addition.
✅ Answer: A is true, R is true, and R correctly explains A.
Q47.
Assertion (A): In mesh analysis, KVL is repeatedly applied.
Reason (R): Each mesh current is an assumed loop current.
✅ Answer: A is true, R is true, and R correctly explains A.
Q48.
Assertion (A): In nodal analysis, KCL is repeatedly applied.
Reason (R): Node voltages relative to reference node are calculated.
✅ Answer: A is true, R is true, and R correctly explains A.
Q49.
Assertion (A): The sign convention for emf and potential drop must be consistent when applying KVL.
Reason (R): Wrong sign convention gives incorrect results.
✅ Answer: A is true, R is true, and R correctly explains A.
Q50.
Assertion (A): KCL and KVL together form the basis of network theorems in circuit theory.
Reason (R): Theorems like Thevenin’s and Norton’s are derived using Kirchhoff’s laws.
✅ Answer: A is true, R is true, and R correctly explains A.
Assertion Reason Questions with Answers | Class 12 physics Important Practice for Board Exams
