Dear Readers, Welcome to Magnetism and Electromagnetism Interview Questions and Answers have been designed specially to get you acquainted with the nature of questions you may encounter during your Job interview for the subject of Magnetism and Electromagnetism. These Magnetism and Electromagnetism Questions are very important for campus placement test and job interviews. As per my experience good interviewers hardly plan to ask any particular questions during your Job interview and these model questions are asked in the online technical test and interview of many IT & Non IT Industries.
An electromagnet is an object that acts like a magnet, but its magnetic force is created and controlled by electricity–thus the name electromagnet. By wrapping insulated wire around a piece of iron and then running electrical current through the wire, the iron becomes magnetized. This happens because a magnetic field is created around a wire when it has electrical current running through it. Creating a coil of wire concentrates the field. Wrapping the wire around an iron core greatly increases the strength of the magnetic field.
When electricity passed through a wire, a magnetic field is created around the wire. Looping the wire increases the magnetic field. Adding an iron core greatly increases the effect and creates an electromagnet. You can create an electromagnet without the iron core. That is usually called a solenoid.
To find the direction the magnetic field is going, you can use the “right-hand rule” to determine it. If you take your right hand and wrap it around the wire, with your thumb pointing in the direction of the electrical current (positive to negative), then your fingers are pointing in the direction of the magnetic field around the wire.
Electromagnetic induction is a process where a conductor placed in a changing magnetic field causes the production of a voltage across the conductor. This process of electromagnetic induction, in turn, causes an electrical current – it is said to induce the current.
Magnetic flux is the magnetic lines of force produced by a magnet. It is measured by the unit weber. A weber (Wb) is equal to 100,000,000 maxwell(s). Flux density (B), a measure of the strength of a wave, is equal to the number of magnetic lines of flux per square meter in terms of the unit tesla (T), where B = Wb/A.
Electromagnetic waves are formed when an electric field couples with a magnetic field. The magnetic and electric fields of an electromagnetic wave are perpendicular to each other and to the direction of the wave.
State the applications of electromagnetism.
A primary electromagnetic device is the relay. The action of the armature, spring, and coil is the same in all relays. Notice, however, the schematics are only different as far as the contacts are concerned. Relays are usually used to control high-voltage switching (contact use) with a low-voltage control application (the coil winding). They may also be used as remote control devices. Relay contacts are normally open (until armature action closes them) or normally closed (until armature action opens them). Contacts have pole configurations similar to switches, and so you should already be familiar with the contact summary.
State Faraday’s Law of EMI.
Faraday’s Law states that “When magnetic flux changes through a circuit, an emf is induced in it which lasts only as long as the change in the magnetic flux through the circuit continues”.
Quantitatively, induced emf is directly proportional to the rate of change of magnetic flux through
the coil. i.e.
Average emf = -NDf/Dt
Where N = number of turns in the coil.
The negative sign indicates that the induced current is such that the magnetic field due to it opposes the magnetic flux producing it.
A. magnetic field is an area surrounding a magnet within which the effects of that field may be observed.
A magnetic field is represented by imaginary lines of force that we call? magnetic flux. Magnetic flux is measured in webers; the intensity of the magnetic flux is called magnetic flux density which is defined as the flux per unit area, measured in webers per square meter, which is given the special name, the tesla.
1. An electric field is a field of force, surrounding a charged particle, while a magnetic field is a field of force surrounding a permanent magnet, or a moving charged particle.
2. The strength of an electric field is expressed in Newtons per Coulomb, or Volts per meter, while a magnetic field strength is expressed in Gauss or Tesla.
3. The force of an electric field is proportional to the electric charge, while the magnetic field is proportional to the electric charge as well as the speed of the moving charge.
4. Electric and magnetic fields oscillate at right angles to one another.
A transformer makes use of Faraday’s Law and the ferromagnetic properties of an iron core to efficiently raise or lower AC voltages. It, of course, cannot increase power so that if the voltage is raised, the current is proportionally lowered and vice versa.
Explain Eddy Currents.
An eddy current is a circular current that flows in a solid conductor, such as sheets of metal or rods. When a changing magnetic field is somehow applied to such a conductor, electromagnetic induction occurs. However, since the charges are not bounded by a narrow conductor, the currents flow in circles called eddy currents. The eddy current flows in a closed loop and acts like the current in a coil or solenoid that produces its own magnetic field.
EMI is regulated to allow today’s sensitive equipment to function properly without suffering degradation in performance due to interference generated by the equipment itself as well as the interference generated by other electronic devices. The EMI spectrum is a limited natural resource that must be maintained to allow reliable radio frequency communications. The successful regulation of EMI interference will allow future electronic devices to operate as defined, in the intended environment, without suffering any degradation in performance due to interference, and without disrupting the performance of other equipment.
Magnet is an object, which produces magnetic field around it.
Magnetic field is the region present around a magnet where force of attraction or repulsion is present.
Magnet has two poles:
Magnets are of two types:
Permanent magnet is type of magnet, which does not lose its magnetic field.
Temporary magnet is a type of magnet, which lose its magnetic field after a short period.