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Question : 25
Total: 26
A device ' X V = V 0 s i n ω t
(a) Identify the device 'X
(b) Which of the curves A, B and C represent the voltage, current and the power consumed in the circuit? Justify your answer.
(c) How does its impedance vary with frequency of the ac source? Show graphically.
(d) Obtain an expression for the current in the circuit and its phase relation with ac voltage.
OR
(a) Draw a labelled diagram of an ac generator. Obtain the expression for the emf induced in the rotating coil ofN A
(b) A horizontal conducting rod10 m 5 ⋅ 0 ms − 1 0.3 × 10 − 4 Wb m − 2
Find the instantaneous value of the emf induced in the rod.
(a) Identify the device '
(b) Which of the curves A, B and C represent the voltage, current and the power consumed in the circuit? Justify your answer.
(c) How does its impedance vary with frequency of the ac source? Show graphically.
(d) Obtain an expression for the current in the circuit and its phase relation with ac voltage.
OR
(a) Draw a labelled diagram of an ac generator. Obtain the expression for the emf induced in the rotating coil of
(b) A horizontal conducting rod
Find the instantaneous value of the emf induced in the rod.
Solution:
(a) Identification
(b) Identifying the curves Justification
(c) Variation of Impedance with frequency Graph
(d) Expression for current Phase relation
(a) The deviceX
(b) Curve B→
Curve C→
CurveA →
Reason: The current leads the voltage in phase,by≠ ∕ 2
(c)X c =
( X c α
)
V = V o s i n ω t
q = C V = C V o s i n ω t
I =
= ω c V o cos ω t
= I o s i n ( ω t + π ∕ 2 )
Current leads the voltage, in phase, by≠ ∕ 2
OR
(a)
When thecoil rotatesin a magnetic field, itseffective area, i.e.,A cos θ ϕ = N B A cos θ ω t θ
ϕ = N B A cos ω t ,
Therefore induced emfε = −
⇒ ε = N B A ω s i n ω t
induced emf will be maximum whenω t = 90 ∘
Hence,ε max = N B A ω
The direction of induced emf can be determined using Fleming's right hand rule.
(b) I = 10 m , u = 5 m ∕ s , B = 0.3 × 10 − 4 Wb ∕ m 2
∴ ε = Blv
= 0.3 × 10 − 4 × 10 × 5
= 15 × 10 − 4 V
(b) Identifying the curves Justification
(c) Variation of Impedance with frequency Graph
(d) Expression for current Phase relation
(a) The device
(b) Curve B
Curve C
Curve
Reason: The current leads the voltage in phase,by
(c)
Current leads the voltage, in phase, by
OR
(a)
When thecoil rotatesin a magnetic field, itseffective area, i.e.,
Therefore induced emf
induced emf will be maximum when
Hence,
The direction of induced emf can be determined using Fleming's right hand rule.
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