intro
Question 1:
What is the force exerted on a 7m conductor carrying a 1A current, situated within a 0.3T magnetic field, and oriented parallel to the said field?
Topic: Magnetic Force on a Current-Carrying Conductor
Correct Answer: B) 0N
- The formula to calculate the magnetic force on a current-carrying conductor is F = ILBsinθ, where I = current, L = length of the conductor, B = magnetic field strength, and θ = angle between the direction of the current and the magnetic field.
- In this case, since the conductor is parallel to the field, θ = 0 degrees. Hence, sinθ = 0.
- Substituting values into the formula, F = 1A * 7m * 0.3T * sin0 = 0.
- Therefore, the correct answer is B, "0N".
Question 3:
An electron (with a charge of -1.6x10-19C) is traveling in the positive x-direction at a speed of 3x105 m/s. If a 0.8T magnetic field is present in the positive z-direction, what would be the magnetic force experienced by the electron?
Topic: Force on a Moving Charge in a Magnetic Field
Correct Answer: D) 4x10-14 N, in the positive y direction
- The force experienced by a moving charge in a magnetic field is calculated by F = qvBsinθ.
- In this case, the electron is moving in the x-direction, and the magnetic field is in the z-direction, so θ = 90 degrees.
- Substituting values into the formula, F = -1.6x10-19 C * 3x105 m/s * 0.8T * 1 = -3.84x10-14 N.
- The negative sign indicates the force acts in the opposite direction to the field, which is the positive y-direction.
- Therefore, the correct answer is D, "4x10-14 N, in the positive y direction".
Question 4:
What is the correct value for the permeability of free space, represented by "µo"?
Topic: Magnetic Permeability in Free Space
Correct Answer: A) 4π × 10-7 WbA-1m-1
- The permeability of free space, denoted by µo, is a constant value used in electromagnetic equations.
- The correct value of µo is 4π × 10-7 WbA-1m-1.
- Therefore, the correct answer is A, "4π × 10-7 WbA-1m-1".
MCQ 5:
Identify the graph that accurately represents the magnitude of the magnetic field surrounding an infinitely long, straight wire carrying current, with respect to the distance "r" from the wire.
Topic: Magnetic Field Around a Current-Carrying Wire
Correct Answer: D) Graph D
- The magnetic field around a current-carrying wire decreases with increasing distance from the wire, following an inverse relationship.
- As the distance "r" increases, the magnetic field strength decreases.
- Therefore, the correct graph would be the one that displays this inverse relationship. Hence, the correct answer is D, "Graph D".
MCQ 6:
An electron and a proton, both having the same momentum, enter a magnetic field perpendicularly. If "ra" and "rb" represent the radii of curvatures for the electron and proton respectively, then which is true?
Topic: Movement of Charged Particles in a Magnetic Field
Correct Answer: C) ra = rb
- The radius of curvature for a charged particle moving in a magnetic field is given by r = mv/qB, where m is mass, v is velocity, q is charge, and B is the magnetic field strength.
- In this case, both the proton and electron have the same momentum (mv), and they both experience the same magnetic field (B).
- Therefore, the radius of curvature will be the same for both particles, implying that ra = rb.
MCQ 7:
Two parallel wires with equal currents of 10A attract each other with a force of 1mN. If the current in both wires is doubled, what will be the new force of attraction?
Topic: Magnetic Force Between Current-Carrying Wires
Correct Answer: C) 4mN
- The force between two parallel wires carrying current is directly proportional to the product of their currents.
- If the currents in both wires are doubled, the force of attraction would quadruple (since 2 * 2 = 4).
- Therefore, the correct answer is C, "4mN".
Question 8:
A particle carrying a certain charge is launched into a magnetic field of 10T, with an initial speed of 10m/s at an angle of 60 degrees. If the force acting on the particle is 2.78×10^-17N, which of the following is the charge of the particle?
Topic: Charge of a Particle in a Magnetic Field
Correct Answer: D) 3.20 × 10^-19C
- The magnetic force acting on a charged particle can be calculated using the equation F = qvBsinθ, where q is the charge, v is the speed, B is the magnetic field strength, and θ is the angle at which the particle is moving relative to the field.
- Given that we know F, v, B, and θ, we can rearrange the equation to solve for q: q = F/(vBsinθ).
- Substituting in the provided values gives us the charge of the particle, which matches option D, "3.20 × 10^-19C".
Question 9:
In a cyclotron operating under a specified magnetic field and frequency, if we use "R" to represent the radius of the final orbit, then which of these options correctly describes the relationship between the energy of the particle and "R"?
Topic: Energy of a Particle in a Cyclotron
Correct Answer: B) R²
- In a cyclotron, the energy of a particle is directly proportional to the square of the radius of its final orbit.
- This is expressed as E ∝ R², where E is energy and R is the radius.
- So, the correct answer is B, "R²".
Question 10:
If we symbolize ampere's fundamental dimension as |A|, then which of the following options correctly defines the dimension for the strength of the magnetic field?
Topic: Dimension of Magnetic Field Strength
Correct Answer: B) [MT^-2A^-1]
- The SI unit of magnetic field strength is the Tesla (T), whose dimension is [MT^-2A^-1].
- This dimension is constituted by the mass (M), time (T), and electric current (A).
- Therefore, the correct answer is B, "[MT^-2A^-1]".
Question 11:
The illustration demonstrates a straight wire carrying an electric current in a uniform magnetic field. The magnetic field's direction isn't portrayed, but the magnetic force acting on the wire is indicated by an arrow. Which of the following alternatives correctly identifies the magnetic field's direction?
Topic: Direction of Magnetic Field
Correct Answer: D) Out of the page
- The right-hand rule can be used to establish the magnetic field's direction.
- If the thumb represents the current's direction and the fingers represent the magnetic field, the palm's direction indicates the force on a positive charge.
- The force on the wire is shown in the diagram, so we can reverse engineer the magnetic field's direction.
- This leads us to conclude that the magnetic field direction is out of the page, corresponding to option D, "Out of the page".
Question 12:
The ratio of charge to mass (e/m) for an electron is represented by which of the following formulas?
Topic: Charge to Mass Ratio of an Electron
Correct Answer: B) e/m = 2(V/B²r²)
- The ratio of charge to mass, or specific charge, of an electron can be calculated through certain derivations in the theory of cyclotrons.
- After considering the energy of an electron and equating it to the magnetic force experienced by it in a magnetic field, we get the relationship e/m = 2(V/B²r²).
- Hence, the answer is B, "e/m = 2(V/B²r²)".
Question 13:
Three wires, spaced equidistantly and perpendicular to the page, are depicted in the diagram. Each wire carries an equal current, with two currents directed out of the page and one directed into the page. How would you order the wires based on the magnitudes of the magnetic forces acting on them, from the smallest to the largest?
Topic: Magnetic Forces on Current-Carrying Wires
Correct Answer: C) 2,1 and 3 tie
- The magnetic forces between the wires depend on the direction of the currents. Currents in the same direction attract each other, while currents in opposite directions repel each other.
- Wire 1 and wire 3 will experience the same force due to their currents being in the same direction, while wire 2 will experience a different force due to the current being in the opposite direction.
- Therefore, the correct order from least to greatest force is 2, then 1 and 3 tied, corresponding to option C, "2,1 and 3 tie".
Question 14:
Suppose there exists a proton traveling at a velocity denoted by "v" in a magnetic field that is perpendicular to the proton's direction and has a flux density of 'B'. If the magnetic field's strength is elevated to twice its original value (2B), the proton continues to traverse the same circular path. What will be the resultant effect on the proton's kinetic energy?
Topic: Kinetic Energy in Magnetic Fields
Correct Answer: C) The kinetic energy will quadruple.
- The kinetic energy of a charged particle moving in a magnetic field is given by the formula: KE = (1/2)mv², where m is the mass and v is the velocity of the particle.
- According to the given problem, the velocity remains constant, but the magnetic field intensifies. This results in a proportionate increase in the kinetic energy.
- As the magnetic field's strength is doubled, the kinetic energy will become four times its original value, corresponding to C, "The kinetic energy will quadruple".
Question 15:
An alpha particle moves in a magnetic field with kinetic energy denoted by "E". What should be the kinetic energy of a proton to follow the same circular path in the magnetic field?
Topic: Kinetic Energy of Charged Particles in Magnetic Fields
Correct Answer: A) E
- The kinetic energy of a charged particle in a magnetic field is determined by its charge and mass, not by the type of particle.
- For a proton to follow the same circular path as an alpha particle in the same magnetic field, its kinetic energy must be the same as the alpha particle.
- Hence, the answer is A, "E".
Question 16:
Consider two long, straight, and parallel wires carrying currents 'I' and '3I' respectively, crossing the x-axis in the same direction as depicted. Where along the x-axis does the combined magnetic field result in zero net magnetic field?
Topic: Magnetic Field due to Current-Carrying Wires
Correct Answer: B) 3
- The magnetic fields created by current-carrying wires are directly proportional to the current and inversely proportional to the distance from the wire.
- The net magnetic field will be zero at a location where the magnetic fields due to the currents 'I' and '3I' have the same magnitude but opposite direction.
- In this case, if the distance from 'I' is 1, the distance from '3I' where their magnetic fields cancel out is 3, making the net magnetic field zero at 'x = 3', which corresponds to option B, "3".
Question 17:
Consider a current-carrying conductor, upon which a force is exerted. If all parameters of the force applied to the conductor are multiplied by two and θ=90o, what effect does this have on the magnetic force?
Topic: Magnetic Force on a Current-Carrying Conductor
Correct Answer: C) The magnetic force is multiplied by eight.
- The magnetic force (F) acting on a current-carrying conductor is given by the formula: F = BIl sinθ, where B is the magnetic field, I is the current, l is the length of the conductor, and θ is the angle between B and I.
- If all parameters (B, I, l) are doubled and θ=90o, then the magnetic force increases eightfold. Therefore, the answer is C, "The magnetic force is multiplied by eight".
MCQs 18:
In the illustration, a straight wire carries an electron flow into the page. The wire is located between the poles of a permanent magnet. What direction does the magnetic force act upon the wire?
Topic: Direction of Magnetic Force
Correct Answer: A) ↑
- The direction of the magnetic force on a current (or electron flow) in a wire is given by the right-hand rule.
- If the thumb points in the direction of the electron flow (opposite to the conventional current), and the fingers point in the direction of the magnetic field, the direction of the force is given by the direction of the palm push.
- In this case, the force is upwards, corresponding to option A, "↑".
MCQs 19:
Due to the current in a straight conductor, what happens to the distance between the magnetic field lines?
Topic: Magnetic Field Around a Conductor
Correct Answer: A) The distance increases as we move away from the conductor.
- The magnetic field (B) surrounding a current-carrying conductor is inversely proportional to the distance (r) from the conductor (B∝1/r).
- As we move away from the conductor, the magnetic field's strength decreases, implying that the distance between the magnetic field lines increases.
- Hence, the correct answer is A, "The distance increases as we move away from the conductor".
MCQs 20:
What is the correct expression for the frequency of a cyclotron?
Topic: Cyclotron Frequency
Correct Answer: C) qB/2πm
- The frequency of a cyclotron, a type of particle accelerator, is determined by the formula: f = qB/2πm.
- In this formula, q is the charge of the particle, B is the magnetic field, and m is the mass of the particle.
- Therefore, the correct answer is C, "qB/2πm".
Question 21:
A proton with charge e, moving perpendicular to a magnetic field, experiences the same force as an alpha particle (charge 2e) moving perpendicularly in the same field. What is the ratio of their speeds, v_proton/v_alpha?
Topic: Speed Ratio of Charged Particles in a Magnetic Field
Correct Answer: C) 2
- The force experienced by a charged particle moving in a magnetic field is given by F = qvBsinθ.
- If the two particles experience the same force and are moving perpendicularly to the field, then their speed ratio is proportional to their charge ratio.
- Therefore, v_proton/v_alpha = e/(2e) = 0.5, which corresponds to answer choice C, "2".
Question 22:
If "F" represents the maximum force exerted on a conductor, what happens to the force when we change the direction of the conductor to make a 45-degree angle with the magnetic field?
Topic: Force on a Conductor in a Magnetic Field
Correct Answer: C) It decreases.
- The force on a current-carrying conductor in a magnetic field is given by F = BIl sinθ, where θ is the angle between the direction of the current and the magnetic field.
- When the angle is less than 90 degrees, the force decreases.
- As a result, when the conductor makes a 45-degree angle with the magnetic field, the force decreases, corresponding to choice C, "It decreases".
Question 23:
The tesla, denoted as "T", is the unit of magnetic flux density. How is it represented? (UHS 2019)
Topic: Units of Magnetic Flux Density
Correct Answer: D) 1 NA-1m-1
- The Tesla (T) is the SI unit for magnetic flux density. It is equal to one Newton per ampere-meter, which is expressed as 1 NA-1m-1.
- This corresponds to answer choice D, "1 NA-1m-1".
Question 24:
Consider the movement of electrons in a wire situated near the North pole of a magnet. In which direction will the wire be propelled?
Topic: Electron Movement in a Magnetic Field
Correct Answer: D) upwards
- The right-hand rule is applied to determine the direction of force when conventional current flows.
- In this scenario, electron flow constitutes the current, which is opposite to the conventional current.
- Hence, according to the right-hand rule, the force direction will be upward.
- This corresponds to option D, "upwards".
Question 25:
Imagine two parallel, straight wires carrying current in the same direction. The wires, separated by 0.40cm, carry currents of 8.0A and 12A, respectively. What is the magnetic field (in tesla) at a point equidistant from both wires?
Topic: Magnetic Field Between Current-Carrying Wires
Correct Answer: C) 4.0×10-4
- The magnetic field between two wires carrying current in the same direction adds up at a point midway between the wires.
- Using the formula for the magnetic field due to a long straight wire, and summing up the contributions from both wires, we can determine the magnitude of the field.
- This corresponds to option C, "4.0×10-4".
Question 26:
Among the options below, which one is a vector quantity?
Topic: Vector Quantities in Magnetism
Correct Answer: D) Both options "A" and "B"
- A vector quantity is one that has both magnitude (size) and direction.
- The density of magnetic flux, denoted as B, and lines of magnetic field, both possess this characteristic.
- This corresponds to answer choice D, "Both options 'A' and 'B'".
MCQs 27:
Which of the following is an essential factor in determining the motion of an electron in a magnetic field?
Topic: Factors Influencing Electron Motion in a Magnetic Field
Correct Answer: D) Ratio of electron's charge to mass
- The motion of an electron in a magnetic field is primarily determined by the ratio of its charge to its mass.
- This ratio dictates how strongly the electron is affected by the magnetic field.
- This corresponds to answer choice D, "Ratio of electron's charge to mass".
MCQs 28:
Which of the following correctly represents the time period of an electron moving in a circular path in a magnetic field?
Topic: Time Period of Electron Motion in a Magnetic Field
Correct Answer: A) 2πm/eB
- The time period of an electron moving in a circular path in a magnetic field is given by the equation 2πm/eB, where m is the electron's mass, e is its charge, and B is the magnetic field strength.
- This corresponds to answer choice A, "2πm/eB".
MCQs 29:
An electron that is moving perpendicular to a magnetic field follows a circular path with a radius 'r'. If the electron's velocity is doubled and the magnetic field's strength is halved, what will be the new radius of the electron's circular path?
Topic: Electron Motion in Magnetic Field
Correct Answer: D) 4r
- The radius of the circular path of an electron in a magnetic field is directly proportional to its velocity and inversely proportional to the magnetic field strength.
- When the electron's velocity doubles and the magnetic field strength halves, the new radius will be four times the original.
- Thus, the answer is D, "4r".
MCQs 30:
You see a wire carrying a current 'I' situated between the poles of a magnet. In which direction will the force on the wire be exerted?
Topic: Current-Carrying Wire in a Magnetic Field
Correct Answer: B) Downward
- According to the right-hand rule, the direction of force on a current-carrying wire placed in a magnetic field will be perpendicular to both the wire and the magnetic field.
- In this case, the force acts downwards.
- Thus, the correct answer is B, "Downward".
MCQs 31:
Suppose you have a wire of length 'L' with a cross-sectional area of 'A'. The wire carries 'n' charge carriers per unit volume, each moving with a velocity 'v'. How is the current flowing through the wire represented?
Topic: Current in a Conductor
Correct Answer: A) nAqv
- The current 'I' through a conductor is given by the formula I = nAqv, where 'n' is the number of charge carriers in unit volume, 'A' is the cross-sectional area of the wire, 'q' is the magnitude of charge on each charge carrier, and 'v' is their velocity.
- The correct response is A, "nAqv".
MCQs 32:
What is the orbit radius of an electron that is traveling at a speed of 2.0×10^7 ms^-1 within a steady magnetic field of 1.20×10^-3 T?
Topic: Electron Orbit Radius in a Magnetic Field
Correct Answer: A) 9.4 × 10^-2 m
- The radius of an electron's orbit moving within a uniform magnetic field is calculated by the formula r = mv/qB, where m is the mass of the electron, v is its velocity, q is the charge of the electron, and B is the magnetic field strength.
- By substituting the given values into the formula, you will find the correct answer to be A, "9.4 × 10^-2 m".
Question 33:
Consider a particle of mass 'm' that is free to traverse an electric field. What would represent its acceleration?
Topic: Particle Acceleration in Electric Field
Correct Answer: A) qE/m
- The acceleration of a freely moving charge in an electric field is given by the formula a = qE/m, where q is the charge of the particle, E is the electric field strength, and m is the mass of the particle.
- Thus, the correct answer is A, "qE/m".
Question 34:
An electron (charge = -1.6×10^-19 C) is moving in the xy plane at a specific moment, with velocity components vx = 5×10^5 m/s and vy = 3×10^5 m/s. A 0.8T magnetic field is present in the positive x direction. What is the magnetic force acting on the electron at that moment?
Topic: Magnetic Force on Electron
Correct Answer: C) 3.8×10^-14 N
- The magnetic force on a moving charged particle is calculated by the equation F = qvB sin θ, where q is the charge of the particle, v is its velocity, B is the magnetic field strength, and θ is the angle between the velocity and the magnetic field.
- With the given values, and considering that the magnetic field is perpendicular to the velocity (θ = 90 degrees), you can determine the correct answer to be C, "3.8×10^-14 N".
Question 35:
An α particle and a proton are both launched into a uniform magnetic field in such a way that their trajectories are perpendicular to the field lines. If both particles travel along circular paths of the same radius, what is the ratio of their momenta PP/Pα?
Topic: Momentum of Charged Particles in Magnetic Field
Correct Answer: B) 1/2
- The momentum of a particle moving in a circular orbit within a magnetic field is given by the formula p = qvB, where q is the charge of the particle, v is the velocity, and B is the magnetic field strength.
- Since both particles are traveling in circles of equal radius, their velocities are proportional to their charges, which are the same, and thus their momenta are proportional to their masses.
- A proton has a mass approximately 1/2 that of an α particle, so the answer is B, "1/2".
MCQs 36:
How does the magnetic field strength around a straight, current-carrying conductor change with radial distance?
Topic: Magnetic Field around Conductors
Correct Answer: A) It is inversely proportional to the radial distance
- According to Ampere's Law, the magnetic field strength 'B' around a straight current-carrying conductor depends inversely on the radial distance 'r', i.e., B ∝ 1/r.
- So, the correct answer is A, "It is inversely proportional to the radial distance".
MCQs 37:
What is the unit of the permeability of free space?
Topic: Permeability of Free Space
Correct Answer: C) A-1Wbm-1
- The permeability of free space, denoted as µ0, is a measure of a material's ability to conduct magnetic fields. In the International System of Units (SI), its value is 4π×10^-7 WbA-1m-1.
- Hence, the correct choice is C, "A-1Wbm-1".
MCQs 38:
What is the expression for the force per unit length on a current-carrying conductor in terms of current (I), length (L), and angle (θ)?
Topic: Force on Conductor
Correct Answer: D) IBsinθ
- The force per unit length on a current-carrying conductor in a magnetic field is defined as F/L = IBsinθ. This equation takes into account the current (I), magnetic field strength (B), and the angle between the direction of current and the magnetic field (θ).
- Therefore, the answer is D, "IBsinθ".
MCQs 39:
Under what condition is the force exerted on a current-carrying conductor by a magnetic field at its peak?
Topic: Force on Conductor
Correct Answer: C) 90 degrees
- The force acting on a current-carrying conductor in a magnetic field is determined by the formula F = ILBsinθ.
- The force (F) is maximum when sinθ equals 1, which happens when θ is 90 degrees.
- Consequently, the right answer is C, "90 degrees".
MCQs 40:
What is the formula for the force on a current-carrying conductor moving in a uniform magnetic field?
Topic: Force on Conductor
Correct Answer: C) F=ILBsinα
- The force exerted on a current-carrying conductor of length L, carrying current I, and moving in a magnetic field B, is given by F = ILBsinα.
- Here, α is the angle between the direction of the current and the magnetic field.
- Thus, the correct answer is C, "F=ILBsinα".
MCQs 41:
Out of an electron, a proton, an alpha particle, and each moving with the same speed into a uniform magnetic field perpendicularly, which one experiences the greatest deflection?
Topic: Deflection of Charged Particles in a Magnetic Field
Correct Answer: A) Electron
- The deflection of a charged particle in a magnetic field is inversely proportional to its mass, given the same charge and speed.
- As the electron has the smallest mass among the given particles, it will be deflected the most.
- Therefore, the correct answer is A, "Electron".
Question 42:
If the horizontal component of the Earth's magnetic flux density is 1.8×10-6T and a horizontal conductor carries a current of 160A, what is the maximum force per unit length?
Topic: Force on Conductor in a Magnetic Field
Correct Answer: A) 2.88 × 10-4 N/m
- The maximum force per unit length (F/L) on a current-carrying conductor in a magnetic field is given by the formula F/L = IB, where I is the current and B is the magnetic field strength.
- By substituting the given values of I (160A) and B (1.8×10-6T), we find F/L = 2.88 × 10-4 N/m.
- Therefore, the correct answer is A, "2.88 × 10-4 N/m".