Previous Year Questions- Time Varying Fields | Electromagnetic Fields Theory (EMFT) - Electrical Engineering (EE) PDF Download

Q1: A rotating conductor of 1 m length is placed in a radially outward (about the z-axis) magnetic flux density (B) of 1 Tesla as shown in figure below. Conductor is parallel to and at 1 m distance from the z-axis. The speed of the conductor in r.p.m. required to induce a voltage of 1 V across it, should be __________.      (SET-2 (2016))
(a) 2.62
(b) 8.34
(c) 7.75
(d) 9.55
Ans: (d)
Sol: Voltage insuced
(where E_m is induced electric field)
Since,
Volatage induced = 1 V
where, V = (radius of path) x (angular velocity)
Now from this we get

Q2: A circular turn of radius 1 m revolves at 60 rpm about its diameter aligned with the x-axis as shown in the figure. The value of μ₀ is  4π × 10⁻⁷ in SI unit. If a uniform magnetic field intensity  is applied, then the peak value of the induced voltage, V_turn ( in Volts), is _________.       (SET-2  (2015))
(a) 150.35
(b) 200.25
(c) 248.05
(d) 300.54
Ans: (c)
Sol: The circular turn rotate with 60 rpm, let the angle made by ring w.r.t. x-axis θ
and θ = ω₀t
the turn rotate at 60 rpm,  
so, ω₀ = 2π
So, the flux flowing through the circular turn wil be

Q3: Consider a one-turn rectangular loop of wire placed in a uniform magnetic field as shown in the figure. The plane of the loop is perpendicular to the field lines. The resistance of the loop is 0.4 Ω, and its inductance is negligible. The magnetic flux density (in Tesla) is a function of time, and is given by B(t) = 0.25 sin ωt, where ω = 2π × 50 radian/second. The power absorbed (in Watt) by the loop from the magnetic field is ________.         (SET-1 (2015))
(a) 0.11
(b) 0.34
(c) 0.96
(d) 0.19
Ans: (d)
Sol: