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Unformatted text preview: PHY124 Magnetic Force II Exp. 4b Abstract In this experiment a simple current balance will be used to measure the force on a current-carrying wire in a magnetic field. The magnetic field is produced by a solenoid, and from the magnitude of the force on the wire the number of turns in the solenoid will be calculated. 1 Knowledge, Understanding, and Skills You should have a “hands-on” experience and ability with all the following: • The concept of magnetic moment. • The concept of magnetic torque. • How to change balance readings into torques. • The formula for magnetic field of a helmholtz coil. 2 Equipment • 5 A Power Supply, • Helmholtz Coils • 500 mA Power Supply, • 5A Current shunt, • 2 Digital Multimeters • Electronic weight scale, • 100-turn triangular coil with balance arm. 3 Method The torque balance is shown schematically in Figure 1. The balance arm is a thin rectangular insulator upon which a 100-turn triangular coil is mounted. The coil is balanced by a weight resting on the pan of PHY124 Magnetic Force II Exp. 4b Figure 1: Here is a sketch of the lab setup. electronic scale. A small counterweight (a short piece of wire) is hung from the hook near the small coil to provide a gravitational torque τ g , about an axis through the attachment point of the main weight, and will be counter-balanced by the magnetic torque τ B produced when current flows in the 100-turn coil in the presence of the horizontal magnetic field near the center of the Helmholtz coils.presence of the horizontal magnetic field near the center of the Helmholtz coils....
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- Spring '09
- Magnetic Field, Magnetic Torque, Helmholtz coils, small coil, gravitational torque