[PHY] Chapter 22 - Electromagnetic Induction

DARRELL ER (COPYRIGHTED) © TOPIC 22: ELECTROMAGNETIC INDUCTION DARRELL ER (COPYRIGHTED) ©

CHAPTER ANALYSIS THE ABOUT MASTERY EXAM WEIGHTAGE DARRELL ER (COPYRIGHTED) ©

FARADA Y’S LAW LEN’S LAW FLEMING’S RIGHT HAND RULE KEY CONCEPT DARRELL ER (COPYRIGHTED) ©

FARADAY’S LAW Faraday’s Law of electromagnetic induction states that the magnitude of the induced e.m.f is proportional to the rate of change of magnetic flux through the circuit. (Or proportional to the rate at which the magnetic field lines are cut) Magnitude of induced e.m.f increases: Increasing the speed of magnet moving through the coil Stronger magnet Increase number of turns on coil DARRELL ER (COPYRIGHTED) © FARADA Y’S LAW

LEN’S LAW Len’s Law of electromagnetic induction states that the induced current is always in the direction that opposes the change producing it. DARRELL ER (COPYRIGHTED) © LEN’S LAW *Right hand grip rule! Thumb points to the north!

FLEMING’S RIGHT HAND RULE When a moving wire cuts across a perpendicular magnetic field, we can deduce the direct of the current using Fleming’s Right Hand rule. *Similar to Left Hand rule but direction of current is reversed! DARRELL ER (COPYRIGHTED) © FLEMING’S RIGHT HAND RULE

ALTERNATING CURRENT GENERATOR TRANSFORMERS FULL WAVE & HALF WAVE RECTIFICATION KEY CONCEPT DARRELL ER (COPYRIGHTED) ©

Steps: 1. As it rotates in a clockwise manner, it cuts through the magnetic field & an induced current is generated. 2. By Fleming’s Right Hand rule, an induced current will flow in a clockwise manner around the coil. 3. The induced current flows through two slips rings which are connected to the main circuit by the carbon brushes. 4. As the coil rotates beyond 180°, it continues to rotate in a clockwise manner. However, direction of the current induced in both the coil and the circuit will be reversed. 5. Since the direction of the current changes every time the coil passes the horizontal position, the current is known as ‘alternating current’. DARRELL ER (COPYRIGHTED) © ALTERNATING CURRENT GENERATOR

VOLTAGE OUTPUT OF A.C GENERATOR The voltage output of an A.C generator can be measured using a cathode-ray oscilloscope. Magnitude of induced emf can be increased by: • Increasing speed of rotation of the coil • Increasing number of turns of the coil • Using a soft iron core to concentrate the magnetic field lines through the coil • Using stronger magnets DARRELL ER (COPYRIGHTED) © ALTERNATING CURRENT GENERATOR

TRANSFORMERS Transformers comprise of two separate circuits, connected via a soft iron core which runs through the coils of the two circuits. As the main voltage for every country is fixed, the transformers are necessary to increase (step up) or decrease (step down) the input voltage such that the output voltage can be suitable for different electrical appl