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Section 17.1 Induced voltage and induced current • Magnet moving near coil • Conducting wire moving in magnetic field 17.1 Induced voltage and induced current (SB p. 142) Magnet moving near coil light-beam galvanometer Expt. 17B

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## Section 17.1 Induced voltage and induced current

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**Section 17.1Induced voltage and induced current**• Magnet moving near coil • Conducting wire moving in magnetic field © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 142)**Magnet moving near coil light-beam galvanometer Expt. 17B Electromagnetic inductionA. Induced current in a coil coil magnet Go to Quiz Go to Discussion 1 © Manhattan Press (H.K.) Ltd.**A current-time graph**17.1 Induced voltage and induced current(SB p. 143) Magnet moving near coil Expt. 17A Electromagnetic induction(data-logging)A. Induced current in a coil bar magnet data-logging interface coil current sensor © Manhattan Press (H.K.) Ltd.**S**N induced voltage 17.1 Induced voltage and induced current(SB p. 143) Magnet moving near coil change of magnetic field induced current electromagnetic induction © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 143)**Faraday's law Faraday's law of electromagnetic induction conductor +change of magnetic field induced voltage strength of voltage rate of change of magnetic field © Manhattan Press (H.K.) Ltd.**S**N 17.1 Induced voltage and induced current(SB p. 144) Direction of induced current – Lenz's law Lenz's law induced current flows in a directionopposes the change producing it induced current © Manhattan Press (H.K.) Ltd.**repel N-pole**of the magnet 17.1 Induced voltage and induced current(SB p. 144) Direction of induced current – Lenz's law repulsive force N © Manhattan Press (H.K.) Ltd.**attract N-pole**of the magnet 17.1 Induced voltage and induced current(SB p. 144) Direction of induced current – Lenz's law attractive force S © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 145)**Direction of induced current – Lenz's law no force at rest no current © Manhattan Press (H.K.) Ltd.**S**N 17.1 Induced voltage and induced current(SB p. 145) Factors affecting the magnitude of induced voltage magnitude of induced voltageby (1) moving magnet faster (2) using stronger magnet (3)no. of turns of coil © Manhattan Press (H.K.) Ltd.**(a)**(b) (c) 17.1 Induced voltage and induced current(SB p. 146) Example 1: An aluminium ring vertically above a bar magnet falls through it as shown. Draw the induced current in the ring when (a) the ring is moving towards the magnet, (b) the magnet is inside the ring, and (c) the ring is moving away from the magnet. Solution © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 146)**Conducting wire moving in magnetic field Expt. 17B Electromagnetic inductionB. Induced current in a long wire light-beamgalvanometer long wire slab-shapedmagnets on an iron yoke © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 147)**Conducting wire moving in magnetic field data-logging interface Expt. 17A Electromagnetic induction(data-logging)B. Induced current in a long wire longwire current sensor slab-shaped magnets on an iron yoke © Manhattan Press (H.K.) Ltd.**motion**field current 17.1 Induced voltage and induced current(SB p. 148) Fleming's right hand rule Fleming's right hand rule © Manhattan Press (H.K.) Ltd.**motion**current field 17.1 Induced voltage and induced current(SB p. 148) Fleming's right hand rule © Manhattan Press (H.K.) Ltd.**field**current motion 17.1 Induced voltage and induced current(SB p. 148) Fleming's right hand rule © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 149)**Fleming's right hand rule no current CAL Workshop 1 Induced voltage in a conducting wire Thinking 1 © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 149)**Factors affecting the magnitude of induced voltage (1) move the wire faster © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 149)**Factors affecting the magnitude of induced voltage (2) use wire with more turns © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 149)**Factors affecting the magnitude of induced voltage (3) use stronger magnet Go to Activity 1 © Manhattan Press (H.K.) Ltd.**(a)**The induced current flows in an anticlockwise direction. (b) There is no current flowing through the coil. (c) The induced current flows in a clockwise direction. 17.1 Induced voltage and induced current(SB p. 150) Example 2: A conducting loop moves across a magnetic field as shown. Draw the direction of induced current in the loop (if any) in each case. (b) (a) (c) Solution © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 151)**Class Practice 1: 1. In which direction does the induced current flow (if any) when the conductor or magnet is moved in the ways as shown? Note that the arrows in (c) and (d) show the movements of the magnets. Mark the direction of the current (if any) in each of the following diagrams. Answer (a) (b) © Manhattan Press (H.K.) Ltd.**No current**17.1 Induced voltage and induced current(SB p. 151) Class Practice 1: (Cont) 1. (c) Answer (d) (e) © Manhattan Press (H.K.) Ltd.**induced current**metal frame 17.1 Induced voltage and induced current(SB p. 152) Class Practice 1: (Cont) 2. When a copper rod is moving along a metal frame, an induced current flows as shown. (a) In which direction is the copper rod moving? Answer By Fleming's right hand rule, the copper rod is moving to the left. © Manhattan Press (H.K.) Ltd.**induced current**metal frame 17.1 Induced voltage and induced current(SB p. 152) Class Practice 1: (Cont) 2.(b) Due to the induced current, the rod experiences a force inside the magnetic field. In which direction does this force act on the rod? Answer By Fleming's left hand rule or Lenz's law, the force on the rod acts to the right. It opposes the motion of the rod. © Manhattan Press (H.K.) Ltd.**To section 17.2**© Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 140)**Quiz 1.Which of the following statements about coal-burning power plants and nuclear power plants is incorrect? Answer A. Coal-burning power plants generate direct current (d.c.) but nuclear power plants generate alternating current (a.c.). © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 140)**Quiz (Cont) 2.Which of the following cannot be achieved by a simple transformer (power adapter)? Return to Text Answer C. Convert 220 V d.c. to 12 V d.c. © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 141)**Discussion 1:In 1831, Michael Faraday (1791 – 1867) discovered that a current could be produced by moving a conductor through a magnetic field. The conductor was connected in a closed circuit. His discovery turned electricity from a scientific curiosity into a powerful technology. © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 141)**Discussion 1: (Cont)One day, the Prime Minister of England came to see the demonstration of electricity. After that, he asked Faraday what electricity was good for. Do you know how did Faraday reply? If you were Faraday, how would you reply? Discuss with your classmates. Answer © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 141)**Discussion 1: (Cont) After the Prime Minister of England asked what electricity was good for, Faraday replied that he did not have the answer yet, but he did know that one day the Prime Minister would put a tax on it. Return to Text © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 149)**Thinking 1 In what situations does the electromagnetic induction happen? Answer 1. Move a magnet near a conductor. 2. Move a conductor inside a magnetic field. 3. Change the magnitude of a magnetic field. Return to Text © Manhattan Press (H.K.) Ltd.**17.1 Induced voltage and induced current(SB p. 150)**Activity 1 Fleming's right hand rule Let's start: 1. Draw a card from the above pack of 6 cards to represent the direction of the magnetic field. Into the paper 2. Then draw another card to represent the direction of the motion. To left © Manhattan Press (H.K.) Ltd.**field**(into the paper) motion (to left) current 17.1 Induced voltage and induced current(SB p. 150) Activity 1 (Cont) Fleming's right hand rule 3. By Fleming's right hand rule, find the direction of the induced current. 4. Sketch a diagram to show the directions of the magnetic field, motion and induced current. Into the paper To left Return to Text © Manhattan Press (H.K.) Ltd.

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