What are the methods of producing induced emf?
The induced emf can be produced by changing :
- (i) the magnetic induction (B),
- (ii) area enclosed by the coil (A) and.
- (iii) the orientation of the coil (θ) with respect to the magnetic field.
What is the use of induced emf?
A motor has coils turning inside magnetic fields, and a coil turning inside a magnetic field induces an emf. This emf, known as the back emf, acts against the applied voltage that’s causing the motor to spin in the first place, and reduces the current flowing through the coils.
Can you induce an EMF in an open circuit?
Yes, Emf can exist without current flow. Consider ohm’s law: V= IR ; V= Induced EMF For open circuit, R-> infinity Hence, I=V/infinity =0 even for some non-zero value of V. It is same as an isolated cell. An EMF will only be induced in a wire if it passes through a changing magnetic field.
What is the polarity of induced emf?
Lenz’s Law states that the induced emf resulting from a changing magnetic flux has a polarity that leads to an induced current whose direction is such that the induced magnetic field opposes the original flux change.
What is meant by polarity of induced emf?
When an emf is generated by a change in magnetic flux according to Faraday’s Law, the polarity of the induced emf is such that it produces a current whose magnetic field opposes the change which produces it. If it is decreasing, the induced field acts in the direction of the applied field to try to keep it constant.
What is meant by polarity?
1 : the quality or condition inherent in a body that exhibits opposite properties or powers in opposite parts or directions or that exhibits contrasted properties or powers in contrasted parts or directions : the condition of having poles.
What is eddy current and its application?
Strong eddy currents are set up in the metal produce so much heat that the metal melts. This process is used in extracting a metal from its ore.The arrangement of heating the metal by means of strong induced current is called the induction furnace. (2)-Induction motor, the eddy currents may be used to rotate the rotor.
What is difference between induced current and current?
Answer. Both are current flow but generally speaking you have induced current in a conductor if it is in close proximity to another conductor. Current flow in a conductor produces a magnetic field around the conductor. Any other conductor moving through that magnetic field will have a current induced in it.
Is eddy current induced current?
Eddy currents are induced circular currents in conductors exposed to an AC magnetic field. The term is often used for induced currents that cause unwanted heating and losses in conductors, e.g. in transformers and electrical machines.
What are the advantages of eddy current?
The advantages of eddy current testing are: Sensitivity to surface defects. Able to detect defects of 0.5mm in length under favourable conditions. Can detect through several layers.
What is eddy current losses?
Eddy current loss is conductive I2R loss produced by circulating currents induced in response to AC flux linkage, flowing against the internal resistance of the core.
Why do eddy currents produce heat?
An alternating current flowing through a coil (A) generates a magnetic field (B). Placing a workpiece (C) within the field induces eddy currents which will create heat, due to the resistance of the material. Heat is produced where—and only where—these eddy currents flow.
What are eddy currents How can they be reduced?
The eddy’s current are a cause of energy loss in alternating current (AC) inductors, transformers, electric motors and generators and other AC appliances or machinery they are reduced by laminating the magnetic cores. Eddy currents are reduced by using multiple plates instead of using a large plate.
Which of the following is the best method to reduce eddy current?
laminating core
Why eddy currents are considered undesirable?
Undesirable effects of eddy currents: The soft iron core is used in dynamo transformers, motors, generators, etc. When a.c is passed through these instruments the flux changes and eddy currents are set up in the core. Therefore, the core is heated up so the electrical energy is wasted in the form of heat energy.
What are eddy currents and how they are minimized?
Its principle is: When a metallic cylinder (or rotor) is placed in a rotating magnetic field, eddy currents are produced in it. According to Lenz’s law, these currents tends to reduce to relative motion between the cylinder and the field.