Induced e.m.f .

1. Induced e.m.f.

2. Induced e.m.f. • When a conductor moves in a magnetic field an e.m.f. Is induced and a current will flow through the conductor.

3. Coil and magnets ; two coils

4. Laws of Electromagnetic Induction • Faraday’s Law – the magnitude of the induced e.m.f. is directly proportional to the charge of the flux. i.e. the rate at which the conductor cuts the magnetic field. • Lenz’s Law – the direction of the induced e.m.f. is such as to oppose the charge which causes it.

5. When the north pole moves towards the coil the induced current flows so that the north pole is unduced to repel the approaching north pole The induced current direction is such as to produce at the end nearest the magnetic a pole opposes the movement of the magnet

6. Fleming’s right hand rule for induced currents Fleming’s right-hand rule is used when electrical energy is transformed into mechanical energy. Fleming’s right-hand rule is used when mechanical energy is transformed into electrical energy.

7. A.C. Generator • A generator converts mechanical energy into electrical energy. In a simple generator a coil is made to rotate between the poles of a magnet. The ends of the coil are connected to slip rings, and carbon brushes conduct the current to the leads. When the coil is in the vertical position the e.m.f. induced is zero. The coil as now gone through half of a revolution. On the second half of the revolution the direction of the induced e.m.f. changes. During one revolution of the coil an alternating e.mf. is generated.

8. Alternating current generator

9. Current from a simple generator

10. Alternating Current • A generator produces alternating current. The magnitude of the current is continually changing and the direction changes every half cycle. This current had a peak value and an effective or direct current equivalent value