What is the basic property of an electromagnetic wave?
A Frequency
B Perpendicular fields
C Electric field
D Magnetic field
Electromagnetic waves consist of electric and magnetic fields that oscillate perpendicular to each other and to the direction of wave propagation. This is a defining feature of these waves.
What does the term “wave impedance” refer to in an electromagnetic wave?
A Wave speed
B Electric potential
C Wave frequency
D Ratio of electric to magnetic fields
Wave impedance is the ratio of the electric field to the magnetic field in an electromagnetic wave, defining how the wave interacts with the medium through which it travels.
What is the relationship between electric and magnetic fields in a vacuum?
A They are proportional
B They are perpendicular
C They are independent
D They are parallel
In a vacuum, the electric and magnetic fields in an electromagnetic wave are always perpendicular to each other and to the direction of propagation of the wave.
Which of the following is a characteristic of a conductor in an electromagnetic field?
A High resistance
B Low conductivity
C High conductivity
D High permeability
Conductors have high conductivity, meaning they allow the free flow of electric charge, making them ideal for transmitting electromagnetic energy in electrical circuits.
Which of the following is the fastest type of electromagnetic wave in a vacuum?
A Microwaves
B Light waves
C Radio waves
D X-rays
In a vacuum, all electromagnetic waves travel at the same speed, the speed of light, which is approximately 3 × 10^8 meters per second. Light waves are a subset of these waves.
What does Gauss’s law describe?
A Electric flux
B Magnetic field intensity
C Electric field strength
D Magnetic flux
Gauss’s law relates the electric flux through a closed surface to the charge enclosed within that surface. It is one of Maxwell’s equations and applies to electric fields.
What occurs when electromagnetic waves strike a surface at an angle?
A Diffraction
B Absorption
C Refraction
D Reflection
When electromagnetic waves strike a surface at an angle, they are reflected according to the law of reflection, where the angle of incidence equals the angle of reflection.
What is the unit of magnetic field strength?
A Ohm
B Tesla
C Volt
D Ampere
The strength of a magnetic field is measured in teslas (T). One tesla represents a magnetic field that exerts one newton of force per meter on a charged particle.
What type of electromagnetic waves are used for cooking in microwave ovens?
A Radio waves
B X-rays
C Infrared waves
D Microwaves
Microwaves are used in microwave ovens because their frequency is absorbed by water molecules, which heats food. These waves are part of the electromagnetic spectrum, with wavelengths shorter than radio waves.
What is Faraday’s law primarily concerned with?
A Wave propagation
B Magnetic field generation
C Induced electric current
D Electric flux
Faraday’s law states that a changing magnetic flux induces an electromotive force (EMF) in a conductor. This is the principle behind electric generators and transformers.
In electromagnetic theory, what does the term “permittivity” refer to?
A Ability to resist light
B Ability to allow electric field lines
C Resistance to magnetic field
D Ability to conduct electric current
Permittivity is a material property that describes how an electric field interacts with a medium. It measures the material’s ability to permit electric field lines to pass through it.
What is a key function of a waveguide in electromagnetic systems?
A Guide waves
B Amplify waves
C Absorb waves
D Reflect waves
A waveguide is a structure used to guide electromagnetic waves, usually in a specific direction. It is widely used in microwave and optical communication systems to direct wave propagation.
What is the primary effect of electromagnetic interference (EMI)?
A Signal refraction
B Signal reflection
C Signal enhancement
D Signal distortion
Electromagnetic interference (EMI) disrupts the normal operation of electronic devices by causing unwanted disturbances in the signal. It can be generated by various sources like motors and radio waves.
What does the term “displacement current” describe?
A Magnetic current
B Change in current
C Current due to varying electric fields
D Current in conductors
Displacement current is a term in Maxwell’s equations used to account for the changing electric field in capacitors. It behaves like current and plays a role in maintaining the continuity of electric fields.
Which of these is used to reduce the effect of electromagnetic interference?
A Shielding
B Reflection
C Diffraction
D Polarization
Shielding is used to block or reduce electromagnetic interference (EMI) by creating a barrier that prevents electromagnetic waves from entering or leaving a sensitive area or device.