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What are we doing Today? Ch. 5 Magnetism • Homework Questions Check • Hand in Lab 41-42 • Chapter 5 Notes • In class questions & homework p. 174 Question 19 (b,c) textbook p. 174 Question 20 (a,b) Magnetism (Chapter 5 - p.163) Magnet – An object that can attract other objects containing iron, cobalt or nickel Magnetic Poles Iron filings N The strength of a magnet is concentrated at the ends, called north and south “poles” of the magnet. S W N S Bar magnet N S N E Compass If you cut a magnet in half, you get 2 magnets! Magnetism (Chapter 5 - p.163) Magnetic Field – Is the area of space in which the magnetic force of a magnet can act on another magnet. Magnetic Fields *Magnetic field lines move away from north poles and toward south poles. Magnetic Field Lines We can describe magnetic field lines by imagining a tiny compass placed at nearby points. The direction of the magnetic field B at any point is the same as the direction indicated by this compass. N S Field Lines Between Magnets Unlike poles N Attraction S Leave N and enter S N Like poles N Repulsion Ferromagnetic Substance (p.167) Ferromagnetic materials are materials that have magnetic properties similar to those of iron. They can become permanently magnetized. Examples of ferromagnetic materials are nickel and cobalt. ELECTROMAGNET A magnet with a field produced by an electric current Electromagnetism a moving charge (electricity) produces a magnetic field • More coils of wire= more current = stronger magnet • Bigger battery = stronger magnet • Magnetic field pattern around a straight wire. • The resulting magnetic field lines form concentric circles around the wire. The Right-Hand rule can be used to predict the direction of the magnetic field Magnetic field around a wire carrying current The Electromagnet By the Right Hand Rule, a coil of wire with current flowing in it will create a magnetic field The strength of the magnetic field depends on The amount of current in a wire – More current means stronger magnetic field The number of turns in the coil – More turns means stronger magnetic field The material in the coil – Magnetic materials like iron and steel make the magnetic field stronger The Electromagnet • A simple electromagnet can be made by coiling some wire around a steel nail, and connecting a battery to it. • As current rotates around the nail, a magnetic field is created with the North pole at the bottom and the South pole at the top The Electromagnet • Electromagnets are found in many everyday objects such as – Motors and generators – Doorbells – Speakers – Hard drives – VHS and Audio cassette tapes – Telephones Solenoid (p.169) EST • Solenoid: Is a cylindrical coil of live wire. Magnetic Field of a Solenoid(EST) Look at p.169 in your textbook Classwork • P. 174 Questions 21-25 Exit Question(s) Draw the following circuits and which of the circuits below are connected in series, and which are connected in parallel? Number 1 Answer: Parallel Number 2 Answer: Series Number 3 Answer: Parallel Number 4 Answer: Series The circuit is composed of a 6.0-V battery connected to a 10-Ω resistor. It includes an ammeter and a voltmeter connected to the resistor terminals.(look up in chapter 5 on diagrams of circuits). a) Draw the circuit diagram, including the measuring instruments. Exit Questions 1) The potential difference in a circuit is determined to be 10 volts. If the resistance is 5 ohms, what must the current intensity be? The potential difference in a circuit is determined to be 10 volts. If the resistance is 5 ohms, what must the current intensity be? Answer: 1. Determine what you are looking for. 2. List what you know and don’t know. • V = 10 Volts • R = 5 ohms • I =? 3. Use equation V = R x I Solve for I, so I = V/R 4. I = 10 Volts / 5 ohms = 2 A Answer: The current intensity will be 2 A (Amps) What To Do Now?