Draw a labelled diagram of AC generator. Derive the expression for the instantaneous value of the emf induced in the coil.
The labelled diagram of AC generator is as below:
Let at any moment t the perpendicular vector to the plane of coil makes angle θ with direction of magnetic field (B). So, flux passing through the coil
φ = Bcos θ. An
and θ = ωt
[ω is angular velocity of the coil]
So, φ = n A B cos ωt
If e is the instantaneous induced emf produced in the coil, then
Maximum value or peak value of e is attained when sin ωt = ± 1
∴ emax = nω AB
So, e = emax sin ωt
Since, the value of the sine function varies between +1and −1. So, the polarity of emf changes with time and also, output voltage is sinusoidal in nature.
What is the force between two small charged spheres having charges of 2 x 10-7 C and 3 x 10-7 C placed 30 cm apart in air?
An infinite line charge produces a field of 9 × 104 N/C at a distance of 2 cm. Calculate the linear charge density.
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(a) Estimate the number of electrons transferred (from which to which?)
(b) Is there a transfer of mass from wool to polythene?
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A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is 1.5 × 103 N/C and points radially inward, what is the net charge on the sphere?
A point charge of 2.0 μC is at the centre of a cubic Gaussian surface 9.0 cm on edge. What is the net electric flux through the surface?
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(a) in the outer region of the first plate,
(b) in the outer region of the second plate, and
(c) between the plates?
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(a) A charge q is placed at the centre of the shell. What is the surface charge density on the inner and outer surfaces of the shell?
(b) Is the electric field inside a cavity (with no charge) zero, even if the shell is not spherical, but has any irregular shape? Explain.
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(a) at the mid-point of the line joining the two charges, and
(b) at a point 10 cm from this midpoint in a plane normal to the line and passing through the mid-point.
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