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Transcript of Electromagnetic Induction
4.1 The Concepts of Force and Mass
Electromagnetic InductionYES!We need:Loop (complete circuit)Magnetic Field
I can cause BCan B cause I?
I can cause B B can cause IThere are 3 ways to induce I: 1) Change B
2) Change the area of the
3) Change the orientation of the loop
All these changes cause
Wire is 16cm longB1 = 4.0mTFind magnetic flux if:A) its a squareB)its a rectangle with one side = 2.0m Example 1
Example 1Wire is 16cm longB1 = 4.0mTFind magnetic flux if:A) the square is perpendicular to the fieldB)the square makes a 60o angle with the field
The induced emf resulting from a changing magnetic flux has a polarity that leads to an induced current whose direction is such that the induced magnetic field opposes the original flux change.
BLAH BLAH BLAH
Change of B creates current Current will have its own B around it
INDUCED B always FIGHTS THE CHANGE:
If the flux is growing, it will fight it ( )
If the flux is dying, it will help it ( )
There is a constant magnetic field directed into the page in the shaded region. The fieldis zero outside the shaded region. A copperring slides through the region.
For each of the five positions, determine whetheran induced current exists and, if so, find itsdirection.
How strong is I induced?What does current depend on? (Remember this guy
Where would V come from if there is no battery? Just the wire.No battery = no terminal voltage only emfFARADAYS LAW OF ELECTROMAGNETIC INDUCTION
The average emf induced in a single coil is
The Emf Induced by a Changing Magnetic Field
A coil of wire has an area of 0.0015 m2. A magnetic field is perpendicular to the surface. Initially, the magnitude of the magnetic field is 0.050 T and 0.10s later, it has increased to 0.060 T.Find the average emf induced in the coil during this time.What would be the total emf if we had 20 coils?FARADAYS LAW OF ELECTROMAGNETIC INDUCTION
The average emf induced in coil with N loops is
Motors, generators, transformersME - EPEIn a generator (AC or DC) a loop of wire is rotated in a constant magnetic field (Mechanical energy delivered by a person / falling water, etc.)Rotation of the loop causes (change of magnetic flux)causes emf (with changing polarity in AC-generator and constant polarity in DC generator
or x ? or ? direction of I?
EPE - MEIn a motor, wires with current in a constant magnetic field are moved by magnetic forces.
or x ?direction of I?direction of Fm ?TransformersTwo coils (uh-huh!): a primary and a secondary coil. Emf on the primary coil induces emf on the secondary coil.
Example 1A step-down transformer providing electricity for a residential neighborhood has exactly 2680 turns in its primary. When the potential difference across the primary is 5850 V, the potential difference at the secondary is 120 V. How many turns are in the secondary?Example 2A step-down transformer has 525 turns in its secondary and 12 500 turns in its primary. If the potential difference across the primary is 3510 V, what is the potential difference across the secondary?