What defines the electric field intensity in an electromagnetic wave?
A Electric current
B Force per unit charge
C Charge
D Voltage
Electric field intensity represents the force exerted per unit charge at a point in space. It is a measure of how strong the electric field is in influencing a charge.
The magnetic field intensity is proportional to which of the following?
A Resistance
B Electric field
C Voltage
D Electric current
Magnetic field intensity around a conductor is directly proportional to the electric current flowing through the conductor, as described by Ampere’s Law.
Which of Maxwell’s equations describes the relationship between the electric field and charge distribution?
A Lenz’s Law
B Gauss’s Law
C Faraday’s Law
D Ampere’s Law
Gauss’s law relates the electric flux through a closed surface to the charge enclosed within that surface, providing a direct relationship between charge and the electric field.
What type of electromagnetic waves is used for communication via cell phones?
A X-rays
B Infrared waves
C Microwaves
D Radio waves
Microwaves are used for communication in cell phones because their frequency allows them to carry a large amount of information efficiently over long distances.
Which principle explains the induction of an electric current by a changing magnetic field?
A Lenz’s law
B Faraday’s law
C Ampere’s law
D Gauss’s law
Faraday’s law states that a changing magnetic field induces an electric current in a conductor. This principle is the foundation for electric generators and transformers.
What is the unit of magnetic flux?
A Weber
B Volt
C Ampere
D Tesla
Magnetic flux is measured in webers (Wb), representing the total magnetic field passing through a given area. One weber is equivalent to one tesla meter squared.
What does Gauss’s Law state about the electric flux?
A It varies with distance
B It is constant
C It depends on the magnetic field
D It is proportional to enclosed charge
Gauss’s law states that the electric flux through a closed surface is proportional to the total charge enclosed within that surface. This helps in calculating electric fields.
In an electromagnetic wave, which of the following is true about the electric and magnetic fields?
A They are independent
B They are perpendicular
C They are parallel
D They are in the same direction
In an electromagnetic wave, the electric field and magnetic field oscillate perpendicular to each other and to the direction of wave propagation. This is a fundamental property of electromagnetic waves.
What effect does a dielectric material have in a capacitor?
A Increases resistance
B Decreases resistance
C Decreases capacitance
D Increases capacitance
A dielectric material increases the capacitance of a capacitor by reducing the electric field between the plates, allowing the capacitor to store more charge for a given voltage.
What happens when an electromagnetic wave enters a medium with a higher refractive index?
A Wavelength increases
B Speed increases
C Wave bends toward normal
D Wave bends away from normal
When an electromagnetic wave enters a medium with a higher refractive index, its speed decreases and the wave bends toward the normal. This is due to the change in wave speed in the new medium.
Which of these materials are best for blocking electromagnetic interference (EMI)?
A Insulators
B Magnetic materials
C Dielectrics
D Conductors
Magnetic materials, such as ferrites, are commonly used for shielding against electromagnetic interference (EMI). They help to absorb or redirect EMI, preventing it from affecting sensitive devices.
What is the purpose of the displacement current in Maxwell’s equations?
A To account for changing electric fields
B To reflect waves
C To generate magnetic fields
D To induce electric current
Displacement current accounts for the changing electric field in situations where the electric field varies with time. It is necessary to complete Maxwell’s equations, especially in capacitors where no physical current flows.
What is the characteristic of a perfect electric conductor in terms of electromagnetic waves?
A Polarizes waves
B Absorbs all waves
C Transmits all waves
D Reflects all waves
A perfect electric conductor reflects all incident electromagnetic waves and does not transmit any. This property is used in shielding applications to block external electromagnetic waves.
The term “electromagnetic spectrum” refers to:
A Heat radiation
B Sound wave frequencies
C Range of electromagnetic waves
D All visible light
The electromagnetic spectrum refers to the entire range of electromagnetic waves, including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays, each varying in frequency and wavelength.
Which of the following describes the propagation of electromagnetic waves?
A Through a vacuum
B Only through gases
C Only through liquids
D Only through solids
Electromagnetic waves do not require a medium to propagate. They can travel through a vacuum, as evidenced by light from the sun reaching Earth through space.