An electric current can be produced by electromagnetic induction using a magnet and a coil. In this demonstration a 300 turn coil is used with a permanent magnet to induce a current. Various factors are tried to see how the current can be increased. By Ohm's law, voltage is proportional to the current so we can deduce the factors that influence the magnitude of the induced voltage. VELOCITY: Firstly a single magnet is moved in and out slowly. The reading is +100 microampere (uA) on the approach, zero when stationary, and -100 microampere (uA) when leaving. When the approach is at a higher speed the induced current is about +200 and - 200 uA.
FIELD STRENGTH: When the strength of the magnetic field is increased by using two magnets together with like poles side by side the current increases.
NUMBER OF TURNS (TOTAL AREA OF COIL or LENGTH OF WIRE): When two coils are used the current is greater than when one is used.
ANGLE: when the magnet approaches at 90 degrees to the plane of the loop we see maximum current being induced. When the magnet is parallel to the plane of the loop very little current is induced.
In summary, the EMF increases when there is an increase in magnetic field strength (B), length (L), velocity (v) and angle (theta). This supports the theory that EMF = BLv sin(theta).
Filmed at Moreton Bay College by Dr Richard Walding, author New Century Physics for Queensland, 3rd ed, 2019.
Website: seniorphysics.com/ncp
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