Name: Grade & Section: Score: School: Teacher: Subject: General Physics 2 LAS Writer: JAN JEFFREY R. CAMINA Content Editor: RETCHIE JOY B. PISANA CHRISTINE JOY G. SUA Learning Topic: Electromagnetic Induction; Quarter 3-Week 8 LAS 3 Learning Targets: Identify the factors that affect the magnitude of the induced emf and the magnitude and direction of the induced current. Reference(s): Serway, R. and Faughn, J., 2006. Holt Physics. 10801 N. MoPac Expressway, Building 3, Austin, Texas 78759: Holt, Rineheart and Winston, pp.708-714. Electromagnetic Induction Electromagnetic induction is the process of creating a current in a circuit loop by changing the magnetic flux in the loop. To sum it all, electromagnetic induction can be described by the following statements: 1. The separation of charges by the magnetic force induces an emf (refer to Figure 1 and 2). 2. The angle between a magnetic field and a circuit affects induction (refer to Figure 3). 3. Change in the number of magnetic field lines induces a current Figure 1. When the circuit loop crosses the (refer to attachment A.1). lines of the magnetic field, a current is induced in the circuit, as indicated by the movement of the galvanometer needle. Characteristics of Induced Current Suppose a bar magnet is pushed into a coil of wire. As the magnet moves into the coil, the strength of the magnetic field within the coil increases, and a current is induced in the circuit. This induced current in turn produces its own magnetic field, whose direction can be found by using the right-hand rule. If you were to apply this rule for several cases, you would notice that the induced magnetic field direction depends on the change in the applied field, as seen in figure 4. This can be defined by Lenz' Law, which states that magnetic field of the induced current is in a direction to produce a field that opposes the change causing it. B (out of page) Figure 2. The separation of positive and Faraday's Law negative moving charges by the magnetic force creates a potential difference (emf) States that the magnitude of the emf induced in a circuit is between the ends of the conductor. proportional to the rate of change of the magnetic flux that cuts across the circuit. Sometimes can be broken down into two laws. 1. Electromotive force (emf) is induced whenever a conductor cuts magnetic flux. 2. The magnitude of induced emf is proportional to the relative rate of change of flux: Figure 3. These three loops of wire are Where: e = induced emf (Volt) moving out of a region that has a constant e = N- dt N = # of turns of the conductor magnetic field. The induced emf and current are largest when the plane of the loop is = rate of change of flux (wb/s) perpendicular to the magnetic field (a), smaller Faraday's Law when the plane of the loop is tilted (b), and zero when the plane of the loop and the Based from the 1st law, a voltage can be induced in a conductor if magnetic field are parallel (c). When a bar moved across a magnetic field so that flux cutting results. This is also When a bar magnet is moved toward a coil, the known as the Faraday's Principle. induced magnetic field is similar to the field of a bar magnet with the orientation shown. e = BLv Where: e = induced emf (Volt) P = flux density at the location of the conductor (T) L = length of the wire (m) e = v = relative velocity (m/s) t = time of flux cutting (s) When a bar magnet is moved away from a coil, the induced magnetic field is similar to the field of a bar Activity magnet with the orientation shown If you were given a single coil of conductor just like in figure 1, what factors will you consider and what values will you increase or decrease in order to attain maximum induced emf. Explain and illustrate each. For the rubrics of the activity please refer to attachment A.2 on the next page). Figure 4. Effect on the direction of the induced current when it is moved towards and way from the magnetic field