Udit Gupta is teaching live on Unacademy Plus
ALTERNATING CURRENT Introduction
WELCOME I am your educator, Udit Gupta Today I bring forward one of the most easiest to score topic and introduce it slightly to get a grasp of the topic. In this lesson we will get acquainted with AC current and how an AC generator works. For more lessons and courses, visit the following link: https://unacademy.com/user/udit13
WHAT IS ALTERNATING CURRENT? A current is established in the circuit, when a resistor is connected across the terminals of a battery. This current has a unique direction, and moves via the external resistor from the +ve terminal to the -ve terminal. The magnitude of this current is almost constant. If the direction of the current in a resistor or in any other element changes alternately, the current is called an alternating current.
GRAPHICAL REPRESENTATION In this course, we shall study the alternating current (AC) that varies sinusoidally with time. Such a current is given by: alternating Time
EXPLANATION The current repeats its value after each time interval T 2n/ . This time interval is called the time period. . The current is +ve for half the time period and is-ve for the remaining half period This implies, its direction reverses after each half time period The maximum value of the current io which is called the peak current or the current amplitude
EXPLANATION . To get sinusoidally varying alternating current, we need a source which can generate sinusoidally varying emf. . An AC generator, also called and AC dynamo, can be used as such a source. It converts mechanical energy into electrical energy, producing an alternating emf and hence an alternating current
AC GENERATOR - CONSTRUCTION Magnet The diagram shows us three main parts of the dynamo: > Magnets > Slip rings Brushes Brus Slip-Rings Magnet: It could be a permanent or an electromagnet. The poles of magnet face each other so that a strong magnetic field is produced between the poles.
AC GENERATOR - CONSTRUCTION Armature: It is a coil generally wound over a soft-iron core. The core increases the magnetic field due to its magnetization. The two ends of the coil are connected to two slip rings. The coil together with the rings can rotate in the magnetic field. The axis of rotation is in the plane of the coil but perpendicular to the magnetic field. Brushes: Two graphite brushes permanently touch the slip rings. As the armature rotates, the slip rings slip against the brushes so that the contact is maintained all the time. These brushes are connected to two terminals. The external circuit is connected to these terminals.
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