# (a)Derive an expression for induced emf developed when a coil of N turns, and area of cross -section, A is rotated at a constant angular speed  in uiform magnetic field B.(b) A wheel with 100 metallic spokes each 0.5m long is rotated with speed of 120rev/min in a plane normal to the horizontal component of Earth's magnetic field. If the resultant magnetic field at that plane is  and angle of dip at place is , find the emf induced between the axle and the rim of the wheel.

(a) Deriving the expression for emf when a coil of N turn, and area of cross-section A, is rotated at a constant angular speed  in a uniform magnetic field B.

Let 'A' be the area of each turn of the coil.

'N' be the number of turns in the coil

strength of the magnetic field

......(i)

where  is angular velocity of the coil.

As the coil rotates, angle  change, therefore magnetic flux  linked with the coil changes and hence, an emf is induced in the coil.

therefore,

(b)  We have given the values:

length of metallic spokes (l) =0.5m

Speed or velocity (v) = 120rpm = 2rps

Hence,

(angle of dip)

Now,

Where  is  magnetic field

So,

Hence, the emf induced between the axle and the rim of the will is .

### Preparation Products

##### Knockout NEET Sept 2020

An exhaustive E-learning program for the complete preparation of NEET..

₹ 15999/- ₹ 6999/-
##### Rank Booster NEET 2020

This course will help student to be better prepared and study in the right direction for NEET..

₹ 9999/- ₹ 4999/-
##### Knockout JEE Main Sept 2020

An exhaustive E-learning program for the complete preparation of JEE Main..

₹ 12999/- ₹ 6999/-
##### Test Series NEET Sept 2020

Take chapter-wise, subject-wise and Complete syllabus mock tests and get in depth analysis of your test..

₹ 4999/- ₹ 2999/-