10 Which wire , 1,2 or 3 has the largest magnetic flux?
11 NoteVoltage is also called electromotive force (emf), E.
12 How can current be induced in a loop that is in a magnetic field? By changing the magnetic flux over time.
13 The magnetic flux can be changed by: Changing the orientation of the wire loop in which the current is to be induced (movement).Changing the strength of the magnetic field (change current of wire that causes the field).Changing the area of the coil.
14 1. Movement of the wire (Motional EMF) V = - B Lv sinqL: length of the wireq: angle between v and B
15 2. Electromagnetic Induction by changing the current causing the B-field (thus changing the B-field).
16 QuestionIn the “flying ring” demo, how was the magnetic field “felt” by the copper ring changed?Answer: AC current
17 3. When B is constant and A (area) is changing.
22 What is the direction of the induced current? Lenz’s Law: The induced current has a magnetic field that opposes the original change in flux.Indicated by minus (–) sign in Faraday’s equation.
23 In which direction is the current induced in the loop? Answer: Clockwise, because as the bar moves to the right, more field lines are in the loop. The current should act in the (opposite) direction to weaken the magnetic flux (field).
24 Example: Change in Area What is the direction of the induced current?BeforeAfterThe new smaller area contains less field lines (in the area), so the current will act in direction to strengthen the magnetic field, so the current will be induced clockwise.