Lab8_VanLe

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Jan 9, 2024

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Van Thin Le Professor Xiang Song Phys-2426-51700 25 October 2023 Lab 8: Faraday’s Electromagnetic Lab Part A Theory Please study induction concept to answer the following questions. 1. Discuss magnetic flux and list its equation. Explain Faraday’s law and list its equation. Magnetic Flux: Magnetic flux (Φ) measures the magnetic field passing through a surface and is defined as Φ = B ⋅ A ⋅ cos(θ), where B is the magnetic field strength, A is the surface area, and θ is the angle between the field and the surfaces normal. Faraday's Law: Faraday's law of electromagnetic induction states that the induced electromotive force (emf) in a closed circuit is equal to the negative rate of change of magnetic flux through the circuit, expressed as ε = dϕ dt . It signifies how a changing magnetic field induces a voltage in a conductor, and the negative sign denotes the direction of the induced current, which opposes the change in flux. 2. Discuss Lenz’s law. Apply Lenz’s law to find the directions of induced current for Figure (a) and (b). Which side crossing R (left side of R or right side of R) has higher voltage for case (a) and case (b)? Lenz’s Law states that the induced current in a loop is generated in a direction that produces a magnetic field opposing the change in magnetic flux within the loop's enclosed area. This opposition is represented by the negative sign in Faraday's law.

In (a), when a north pole approaches the coil, the coil responds by creating a virtual north pole to counteract the approaching magnet. This action induces a counterclockwise current concerning the bar magnet. In scenario (b), the coil generates a virtual north pole on the side facing the magnet to attract it when the north pole is moving away. This results in the induction of a clockwise current concerning the bar magnet. In (a), the south pole exhibits a higher voltage when it crosses point R, and in (b), the north pole exhibits a higher voltage when it crosses point R. 3. A circular coil consists of 3 turns of wire with radius r = 3.5 cm. A uniform magnetic field directed perpendicular to the plane of the coil is shown in the figure. From t = 0 to t = 0.032 s, the field changes from 0.0012 to 0.023 T. What is the induced emf during this time interval? e =− NA dB dt ¿ − Nπ r 2 dB dt ¿ − 3 ×π× 0.035 2 × 0.023 − 0.0012 0.032 − 0 ¿ − 7.87 × 10 − 3 V 4. In question 3, if the resistance R = 12 Ω, what is the induced current in this time interval? What is the direction of induced current? Which position has higher voltage V A or V B ? V = IR →I = V R ¿ − 7.87 × 10 − 3 12 = 6.55 × 10 − 4 The current's direction, determined by the right-hand rule, is to the right, signifying a clockwise motion (→). VB exhibits a higher voltage than VA.

Part B Lab Go to PhET website. Click on Simulation/Physics. Under Physics, choose Electricity, Magnets & Circuits. Under Electricity, Magnets & Circuits, Faraday’s Electromagnetic Lab is the 15th simulation (Location might change. A to Z search.). Click to run the Faraday’s Electromagnetic Lab . I. Complete Data Table with Pickup Coil Simulation: Basic Operation for Pickup Coil Simulation: Click Pickup Coil tag on the top. Set the Strength scale to 100% (default 75%). Place check mark on Show Field. Click on the Voltmeter as indicator. Change the Loop turns into N = 1 turn. Keep the Loop area 50% as default. Hold and drag the magnet moving forward and backward completely through the center of coil as fast as you can till you observe the maximum induced voltage, V max , and record in Table. Change the Loop turns into N = 2 turns and repeat the process to complete Data Table 1. Data Table 1: Measure Maximum Induced Voltage Assume the voltmeter (V) scaled as showed in the Figure. Assume the radius of coil r = 3 cm = 0.03 m and area A = π•r 2 . Calculate the time rate change of magnetic field dB/dt = V max /(N•A). Attach a screenshot of N = 1 turn Data from the Simulation to lab report . N (# of loops) V max (V) dB/dt (T/s) 1 1.9 672 2 3.7 654 3 5 589

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