EM-Test-1

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Question 1:

What is the direction of the magnetic field with respect to you if a current carrying conductor is carrying current away from you?





Topic: Magnetic Fields in Electrical Current

Correct Answer: B) Clockwise

Short Hint:
  • Using the "right-hand rule," it is possible to determine the direction of the magnetic field.
  • With this rule, if a current-carrying conductor is moving current away from you, the direction of the magnetic field would be clockwise.
  • Therefore, the correct answer is B, "Clockwise".

Question 2:

What does a uniformly moving electric charge generate?





Topic: Electric and Magnetic Fields in Motion

Correct Answer: C) Both electric and magnetic field

Short Hint:
  • An electric charge in uniform motion is known for creating both an electric field and a magnetic field.
  • So, the correct answer is C, "Both electric and magnetic field".

Question 3:

What happens to a stationary electron when a strong magnetic field is applied?





Topic: Effects of Magnetic Field on Stationary Electron

Correct Answer: C) The electron remains stationary

Short Hint:
  • A stationary electron remains stationary even in the presence of a strong magnetic field since a magnetic field only affects moving charges.
  • Thus, the correct answer is C, "The electron remains stationary".

Question 4:

What is the direction of deflection for a photon passing through a magnetic field?





Topic: Photon Behavior in Magnetic Field

Correct Answer: D) None of the above

Short Hint:
  • Photons, whether viewed classically or in terms of quantized photons, are unaffected by static electrical or magnetic fields since they carry no charge.
  • Therefore, the correct answer is D, "None of the above".

Question 5:

What is the maximum force experienced by a neutron (with a mass equal to a proton, mp = 1.6×10-27 kg), moving in a magnetic field of intensity 1.20×10-3 T at a speed of 2.0×107 m/s?





Topic: Force Experienced by a Neutron in Magnetic Field

Correct Answer: A) 0

Short Hint:
  • The force experienced by a charged particle in a magnetic field can be calculated using the formula F = qvBsinθ.
  • Since the neutron is uncharged (q = 0), the force it experiences is zero, regardless of its speed or the strength of the magnetic field.
  • Therefore, the correct answer is A, "0".

Question 6:

In which of the following circumstances will a plane area's magnetic flux passing through it be half its maximum flux?





Topic: Magnetic Flux and Plane Area Orientation

Correct Answer: B) 45°

Short Hint:
  • The magnetic flux passing through a surface area is directly proportional to the cosine of the angle between the area and the magnetic field.
  • When the angle is 45°, the cosine of the angle is 1/√2, which means the flux is 1/√2 times the maximum.
  • Therefore, the correct answer is B, "45°".

Question 7:

What is the maximum force experienced by a neutron (with a mass equal to a proton, mp = 1.6×10-27 kg), moving in a magnetic field of intensity 1.20×10-3 T at a speed of 2.0×107 m/s?





Topic: Force Experienced by a Neutron in Magnetic Field

Correct Answer: A) 0

Short Hint:
  • Charged particles' force in a magnetic field can be done by applying the formula F = qvBsinθ.
  • However, as a neutron is uncharged (q=0), the force experienced is zero, irrespective of its speed or the intensity of the magnetic field.
  • Hence, the correct answer is A, "0".

Question 8:

In which of the following circumstances will a plane area's magnetic flux passing through it be half its maximum flux?





Topic: Magnetic Flux and Plane Area Orientation

Correct Answer: B) 45°

Short Hint:
  • The magnetic flux passing through a surface area is proportional to the cosine of the angle between the area and the magnetic field.
  • When the angle is 45°, the cosine of the angle is 1/√2, which means the flux is 1/√2 times the maximum.
  • Therefore, the correct answer is B, "45°".

Question 9:

Imagine an electron moving along the positive x-axis in an area with a uniform magnetic field directed towards the positive z-axis. From a point on the positive z-axis, how would you describe its subsequent motion?





Topic: Electron Movement in a Magnetic Field

Correct Answer: C) It moves counter clockwise around a circle in the xy-plane

Detailed Hint:
  • Magnetic fields cause charged particles to move according to the right-hand rule, in which there is a perpendicular force between a positive charge and the magnetic field.
  • As a result, an electron (a negative charge) moving in a magnetic field will experience a force that causes it to move in a circular path.

Question 10:

Which of the following will not be deflected by a magnetic field?





Topic: Magnetic Field Influence on Different Rays

Correct Answer: A) Gamma rays

Detailed Hint:
  • Charged particles are deflected from their paths by magnetic fields.
  • Gamma rays, however, are uncharged electromagnetic waves and therefore are unaffected by magnetic fields.

Question 11:

Consider a conducting wire carrying current situated in a magnetic field. Which equation correctly represents the force exerted on it?





Topic: Force on a Current-Carrying Conductor in a Magnetic Field

Correct Answer: A) F = I (L × B)

Detailed Hint:
  • Current-carrying conductors placed in magnetic fields are forced by the formula F = I (L × B), where I is the current, L is the length of the conductor, and B is the magnetic field.
  • The cross-product (L × B) represents the effective area vector perpendicular to the magnetic field.
  • Therefore, the correct answer is A, "F = I (L × B)".

Question 12:

Magnetic flux density is measured in what unit?





Topic: Units of Magnetic Flux Density

Correct Answer: D) All of them

Detailed Hint:
  • The unit of magnetic flux density can be represented in different forms: Weber per square meter, Tesla, or Newton per Ampere per meter.
  • These units are equivalent and can be used interchangeably in physics problems.
  • Hence, the correct answer is D, "All of them".

Question 13:

A proton, a deuteron, and an alpha particle are accelerated by the same potential difference and then enter a magnetic field perpendicularly. What is the ratio of their kinetic energies?





Topic: Kinetic Energy Ratios in a Magnetic Field

Correct Answer: D) 1 : 1 : 2

Detailed Hint:
  • Charged particles in a magnetic field have constant kinetic energy and can be calculated using the equation KE = qv, where q is the charge and v is the velocity of the particle.
  • Protons, deuterons, and alpha particles have different charges, and thus, when accelerated by the same potential difference, they will have different kinetic energies.
  • Therefore, the correct answer is D, "1 : 1 : 2".

Question 14:

What is the unit used to denote the magnitude of a magnetic field?





Topic: Units of Magnetic Field Strength

Correct Answer: B) Weber per square meter

Detailed Hint:
  • Magnetic field strength, represented as 'B', is measured in Weber per square meter (Wb/m2).
  • This unit represents the magnetic flux (ΦB) per unit area (A), as per the equation B = ΦB/A.
  • Therefore, the correct answer is B, "Weber per square meter".

Question 15:

Who is credited with the experimental validation of the existence of a magnetic field around a current-carrying conductor?





Topic: Experimental Evidence of Magnetic Field

Correct Answer: D) Oersted

Short Hint:
  • It was Oersted who first experimentally confirmed the existence of a magnetic field around a current-carrying conductor.
  • This groundbreaking discovery laid a major foundation for the study of electromagnetism.
  • Therefore, the correct answer is D, "Oersted".

Question 16:

An alpha particle moves parallel to the direction of the magnetic field at velocity 'v' as it enters a magnetic field of strength 'B'. What would be the force experienced by the particle?





Topic: Force on an Alpha Particle in a Magnetic Field

Correct Answer: D) Zero

Short Hint:
  • Magnetic field forces on charged particles are calculated by the equation FB = qvBsinθ, where q is denotes charge, v is the velocity, B is denote magnetic field strength, and θ is the angle between the velocity and the magnetic field.
  • When an alpha particle moves parallel to the magnetic field, the angle θ is 0 degrees, and sin0° = 0.
  • Therefore, the force on the alpha particle is zero, making the correct answer D, "Zero".

Question 17:

How would you arrange the three circular loop configurations on the central axes based on their magnetic field magnitudes?





Topic: Magnetic Fields in Circular Loops

Correct Answer: B) 2, 3, 1

Detailed Hint:
  • The magnetic field in the midpoint between the loops on the central axes is influenced by the direction and magnitude of the current in the loops.
  • Consider the Right-Hand Rule to understand the magnetic field direction and magnitude.
  • Hence, the correct sequence is B, "2, 3, 1".

Question 18:

What would be the characteristic of a capacitor that charges and discharges swiftly?





Topic: Capacitor Charging and Discharging

Correct Answer: A) Small RC value

Detailed Hint:
  • The rate at which a capacitor charges and discharges is determined by the RC (resistance-capacitance) value. A smaller RC value allows the capacitor to charge and discharge more quickly.
  • This is based on the understanding that the time constant (RC) of a circuit is the time it takes for a capacitor to charge to about 63.2% of the maximum voltage or to discharge to about 36.8% of its initial voltage.
  • Therefore, the correct response is A, "Small RC value".

Question 19:

Consider a positively charged particle with a velocity 'v' entering a magnetic field. Which of the trajectories below could it follow?





Topic: Charged Particle Trajectories in a Magnetic Field

Correct Answer: D) Any one of (i), (ii), and (iii)

Detailed Hint:
  • The path of a positively charged particle in a magnetic field can be a straight line, a circular path, or a helix, depending on the angle and velocity of the charged particle as it enters the magnetic field.
  • For example, if the charged particle enters the field parallel to the magnetic field lines (i.e., the velocity is parallel to the magnetic field), it will continue in a straight line because the magnetic force is zero.
  • On the other hand, if it enters perpendicularly, it will move in a circular path, and if it enters at an angle, it will follow a helical path.

Question 20:

If a conductor transports current in a direction away from your position, in which orientation would you observe the associated magnetic field?





Topic: Magnetic Fields Generated by Current Carrying Conductors

Correct Answer: B) Rotating in a clockwise direction

Detailed Hint:
  • The Right-Hand Rule help us to determine the direction of a current-carrying conductor's magnetic field.
  • When your thumb points away from you (in this case, away from the current), your fingers will curl in the direction to magnetic field - clockwise.

Question 21:

How would you describe the nature of magnetic field lines?





Topic: Characteristics of Magnetic Field Lines

Correct Answer: A) Enclosed Curve

Detailed Hint:
  • A magnet's north pole is surrounded by magnetic field lines, which form continuous, closed loops.
  • They do not cross each other.
  • Therefore, the correct answer is A, "Enclosed Curve".

Question 22:

Is there any difference between an electric current carried by a wire and a wire that does not carry one?





Topic: Electrical Charge in Current Carrying Wires

Correct Answer: C) It is electrically neutral

Detailed Hint:
  • A wire that carries electrical current is essentially moving charges.
  • However, the total charge in a wire remains neutral because for each electron (negative charge) moving, there's a positive 'hole' left behind.
  • Hence, despite the flow of electric charges, the overall charge of the wire remains neutral.
  • Thus, the correct answer is C, "It is electrically neutral".

Question 23:

What is the equation describing a particle's linear momentum if it moves along a circular path radially 'r' within a uniform magnetic field 'B'?






Topic: Linear Momentum of a Positively Charged Particle in a Uniform Magnetic Field

Correct Answer: A) qBr

Detailed Hint:
  • The linear momentum of a moving particle can be calculated by considering the balance between the centripetal force and the magnetic force.
  • Here, the equation mv2/r = qvB is applied. Simplifying this equation gives us mv = qBr.
  • Therefore, the linear momentum p, which is given by the product of mass and velocity (mv), is equal to qBr.

Question 24:

What type of particle beam is deflected in a cathode ray oscilloscope?





Topic: Operation Principle of a Cathode Ray Oscilloscope

Correct Answer: C) Electrons

Detailed Hint:
  • A cathode ray oscilloscope, or CRO, works on the basis of deflecting a focused, high-frequency beam of a certain type of particle.
  • In this context, the cathode ray tube primarily consists of an electron gun and electrostatic deflection plates, which are responsible for creating and directing this beam.
  • Hence, the correct response is C, "Electrons".

Question 25:

What is the cause of current flow in metals?





Topic: Cause of Current Flow in Metals

Correct Answer: C) Electrons

Detailed Hint:
  • In conductive materials like metals, electrical current is produced through the movement of a type of subatomic particle.
  • This typically involves the 'flow' of these particles in a particular direction.
  • So, the correct response is C, "Electrons".

Question 26:

What instrument can be utilized to identify the presence of a magnetic field?





Topic: Detection of Magnetic Field

Correct Answer: D) Magnetic compass

Detailed Hint:
  • The tool used to detect a magnetic field is not a device that measures electric current or voltage.
  • Instead, it is an instrument often used in navigation, which responds to the Earth's magnetic field.
  • Therefore, the correct answer is D, "Magnetic compass".

Question 27:

What is the equivalent of 1 weber in other units?





Topic: Weber Conversion

Correct Answer: A) 1 Vs

Short Hint:
  • The Weber (Wb) magnetic flux can be expressed using other units of measurement.
  • It's crucial to remember that 1 Weber is not the same as 1 Tesla per meter, 1 Tesla second, or 1 Volt per second.
  • Hence, the correct answer is A, "1 Vs".

Question 28:

If an alpha particle enters a magnetic field of strength 'B' at a velocity 'v', parallel to the magnetic field, what is the force experienced by the particle?





Topic: Force on Alpha Particle in Magnetic Field

Correct Answer: D) Zero

Short Hint:
  • When a charged particle moves parallel to a magnetic field, the angle between the velocity vector and the magnetic field is zero.
  • The force formula F = qvBsinθ is used in this situation. With θ being 0 degrees, the sinθ becomes zero, rendering the entire force zero.
  • As such, the correct answer is D, "Zero".

Question 29:

What is the standard unit for measuring magnetic flux density?





Topic: Magnetic Flux Density Units

Correct Answer: D) All of the above

Detailed Hint:
  • Flux density per unit area is measured perpendicular to magnetic flow direction.
  • It is typically measured in a variety of units, each of which captures a different aspect of this concept.
  • All options listed here, A, B, and C, are valid units for expressing magnetic flux density. So, the correct answer is D, "All of them".

Question 30:

When an electron enters a uniform magnetic field, with its velocity components neither parallel nor perpendicular to the field, what sort of path does the electron follow?





Topic: The Trajectory of an Electron in a Magnetic Field

Correct Answer: A) Helix

Detailed Hint:
  • The path an electron takes when it enters a magnetic field depends on the angle between the electron's velocity and the direction of the magnetic field.
  • If the angle is 90 degrees, the path is circular; if the angle is 0 or 180 degrees, the path is a straight line.
  • However, if the angle is anything other than 0, 90, or 180 degrees, the electron follows a helical path. Hence, the right answer is A, "Helix".

Question 31:

What is the value of the permeability of free space in SI units?





Topic: Permeability of Free Space

Correct Answer: B) 4π × 10-7 Weber per Ampere meter

Detailed Hint:
  • Permeability of free space, denoted by the Greek letter mu (μ0), is a physical constant used in electromagnetic theory.
  • In the presence of a magnetic field, it indicates how much a material can become magnetized.
  • The SI unit of permeability is Weber per Ampere meter (Wb.A-1.m-1), and the permeability of free space is a known constant, 4π × 10-7 Wb.A-1.m-1. Therefore, the correct answer is B.

Question 32:

Consider two rectangles, both lying in the same plane and carrying equal currents, positioned close to each other as illustrated in the figure. What kind of interaction occurs between the two?





Topic: Interactions Between Current Carrying Loops

Correct Answer: A) They attract each other

Detailed Hint:
  • When two current-carrying loops are near each other, the direction of their currents determines their interaction.
  • If the currents are in the same direction, the loops will attract each other due to the magnetic fields they generate.
  • Thus, the correct answer is A, "They attract each other".

Question 33:

An electron, projected horizontally from the North towards the South, in a uniform horizontal magnetic field that operates from East to West. In which direction would the electron deflect?





Topic: Electron Deflection in a Magnetic Field

Correct Answer: D) Downwards, vertically

Detailed Hint:
  • Using the right-hand rule, one can determine the direction in which a charged particle will deflect in a magnetic field.
  • In this case, the electron, moving from North to South, in a magnetic field from East to West, will be deflected vertically downwards.
  • Hence, the correct answer is D, "Downwards, vertically".

Question 34:

What is the numerical value of the permittivity of free space, represented as "εo"?





Topic: Permittivity of Free Space

Correct Answer: B) 8.85 × 10-12 C2/Nm2

Detailed Hint:
  • Permittivity of free space, denoted by εo, is a critical constant in electrostatics.
  • It represents the ability of a vacuum to permit an electric field.
  • The SI unit of permittivity is C²/N.m² (Coulomb squared per Newton meter squared), and the known constant value for εo is 8.85 × 10-12 C2/Nm2. Therefore, the correct answer is B.

Question 35:

What is the proportional relationship between the effective resistances of two identical resistors when first arranged in a series circuit and then in a parallel configuration?





Topic: Resistances in Series and Parallel

Correct Answer: C) 4:1

Detailed Hint:
  • When resistors are connected in series, their effective resistance (or total resistance) is simply the sum of all resistors. For two identical resistors R, the total resistance would be 2R.
  • For resistors in parallel, the effective resistance is the reciprocal of the sum of the reciprocals of each resistance. So, for two identical resistors R, the effective resistance would be R/2.
  • Hence, the ratio of resistances when the resistors are first in series (2R) then in parallel (R/2) is 4:1, so the correct answer is C, "4:1".

Question 36:

Describe the unit of measurement of magnetic flux in the International System of Units (SI)?





Topic: Units of Magnetic Flux

Correct Answer: A) Weber

Detailed Hint:
  • Magnetic flux is a measure of the total magnetic field which passes through a given area. It is denoted by the Greek letter Phi (Φ).
  • In the International System of Units (SI), the standard unit of magnetic flux is the Weber (Wb).
  • Therefore, the correct answer is A, "Weber".

Question 37:

In the context of the Lorentz force, how can the magnetic force be classified?





Topic: Lorentz Force

Correct Answer: B) Deflecting force

Detailed Hint:
  • An electric and magnetic force combine to exert a Lorentz force on a moving charged particle.
  • The magnetic component of the Lorentz force doesn't perform work directly. Instead, it changes the direction of the particle, hence it is referred to as a deflecting force.
  • Therefore, the correct answer is B, "Deflecting force".

Question 38:

What would be the magnitude of the electrical current in an ideal short circuit?





Topic: Current in a Short Circuit

Correct Answer: B) Infinite

Detailed Hint:
  • In the case of an ideal short circuit, the resistance is zero.
  • According to Ohm's law (I=V/R), if resistance (R) is zero, the current (I) becomes infinite since the current is directly proportional to voltage and inversely proportional to resistance.
  • So, the correct answer is B, "Infinite".

Question 39:

What is the effect of the magnetic force on a charge which remains stationary within a loop carrying an electric current?





Topic: Magnetic Force on Stationary Charge

Correct Answer: A) Zero

Short Hint:
  • Magnetic forces act on moving charges. A stationary charge does not experience a magnetic force.
  • This is according to the Lorentz force law, which states that the force on a stationary charge in a magnetic field is zero.
  • Therefore, the correct answer is A, "Zero".

Question 40:

What happens to a spring when an electric current is passed through it?





Topic: Effect of Current on a Spring

Correct Answer: B) Compresses

Short Hint:
  • When current passes through a spring, the adjacent loops of the spring carry the same current direction.
  • A magnetic interaction occurs when two elements carrying current in the same direction are attracted to each other.
  • Thus, the spring contracts or compresses. So, the correct answer is B, "Compresses".
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