Physics 30 June 01 Diploma Exam

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Unformatted text preview: valid for the question. No response is given. 3 Written Response — 15% 1. You have been given a large permanent magnet with a uniform magnetic field between its poles. In a preliminary experiment, the magnetic field of the permanent magnet was found to be at least 100 times the strength of Earth’s magnetic field. Using concepts discussed in the Physics 30 course, design a procedure to measure the magnitude of the magnetic field. Assume that the space between the poles is large enough to insert any necessary equipment. The description of your procedure must include • a label indicating the direction of the magnetic field between the poles of the magnet below • a list of the materials required • a labelled diagram showing your experimental design • a description of how to obtain the measurements required to calculate the magnitude of the magnetic field • a derivation of the formula used to determine the magnitude of the magnetic field NOTE: Marks will be awarded for the physics principles used in your response and for the effective communication of your response. A complete response should include the following content. The clarity of the response is considered in assigning a mark. Expected Content • Magnetic field direction • Effect of External Magnetic field on a moving charge • Experimental Design Sample Solution N S B 4 Experimental Design Method 1 – Circular Motion List: voltmeter metre stick power supply cathode ray tube Procedure: • place the cathode ray tube so that the electron beam is perpendicular to the magnetic field • connect the power supply to the cathode ray tube • connect a voltmeter in parallel to the power supply, record potential difference. This will be used to determine the speed of the electron • use a metre stick to measure the radius of curvature of the electron beam in the magnetic field Electron beam ××××××× ××××××× ××××××× ××××××× ××××××× × Indicates magnetic field perpendicularly into the page Accelerating voltage V Analysis: Fm = Fc or the magnetic force causes circular motion mv 2 r mv B= qr Bvq = Special Notes: Method 1 • The method of determining the speed of the electrons must be explicit • The method of measuring r must be explicit but does not need to be practical. For example, it is not necessary for the student to explicitly identify how the electron path will be observed • The electron path and magnetic field must be perpendicular • The direction of the magnetic field and path deflection must be consistent 5 Method 2 – Velocity Selector List: metre stick 2 voltmeters power supply variable power supply cathode ray tube with metal plates inside Procedure: • set up the cathode ray tube away from the magnetic field so that the electron beam is undeflected. Mark the position of the beam • record the voltage V1. This will be used to determine the speed of the electron • place cathode ray tube so that the electron beam is perpendicular to the magnetic field • adjust the variable power supply on the plates inside the CRT until the electron beam returns to its original path • record the voltage V2 • measure the distance between the plates in the cathode ray tube. Variable power supply Electron beam V2 Accelerating voltage V1 ××××××× ××××××× ××××××× ××××××× ××××××× × Indic...
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This note was uploaded on 01/14/2014 for the course PHYSICS Physics 30 taught by Professor Quinlan during the Fall '09 term at Centennial High School.

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