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Dynamically Induced e.m.f.

Refer Fig. 30. The e.m.f induced (e) in the conductor is given by:

e = Blv volt                                                                      … (22)

where B = flux density of the magnetic field in tesla,

l = length of the conductor in metres, and

v = velocity of the conductor in m/s.

If the conductor moves at an angle e with the direction of flux then the induced e.m.f.

e = Blv sin

Example 26. A 1.2 m long conductor moves at right angles to a uniform magnetic field of flux density 1.8 Wb / m2 with a velocity of 60 metres / second. Calculate the e.m.f. induced in it.

Find also the value of induced e.m.f. when the conductor moves at an angle of 30° to the direction of the field.

Solution. Given: l = 1.2 m ;

B = 1.8 Wb/m2 ;

v = 60 m/s

(i) Induced e.m.f., e = Blv                                              … [See Fig. 33 (a)]

= 1.8 × 1.2 × 60 = 129.6 V. (Ans.)

(ii) Induced e.m.f., e = Blv sin θ                                   … [See Fig. 33 (b)]

= 1.8 × 1.2 × 60 × sin 30° = 64.8 V. (Ans.)

Example 27. In a four-pole dynamo, the flux/pole is 18 m Wb. If the armature is driven at 600 r.p.m., what is the average e.m.f. induced in one of the armature conductors?

Solution; Flux/pole = 18 m Wb;