Test: Magnetostatics- 2
20 Questions MCQ Test Topicwise Question Bank for Electrical Engineering | Test: Magnetostatics- 2
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A circular conductor of 1 cm radius has an internal magnetic field
where 
, r0 is the radius of the conductor and 
is the unit vector. The total current in the conductor is given by
where
, r0 is the radius of the conductor and is the unit vector. The total current in the conductor is given byBy Ampere's law,
Hence, current enclosed
Given, r0 = 1 cm = 0.01 m
What is the value of mutual inductance between an infinitely long straight conductor along the y-axis and a rectangular single turn coil situated in x-y plane with its corners located at point (a, 0), (a + d, 0), (a, h) and (a + d, h) as shown in figure below?
The mutual inductance is given by
Flux density at any point P in the x-y plane is
and
Assertion (A): The force acting between two parallel wires carrying currents is directly proportional to the individual currents and inversely proportional to the square of the distance between them,
Reason (R): The force is repulsive if the two currents I1 and I2 are in the same directions and attractive if in opposite directions.
Reason (R): The force is repulsive if the two currents I1 and I2 are in the same directions and attractive if in opposite directions.
The force acting between the two parallel wires carrying currents I2 and I2 respectively is given by
Thus,
Hence, assertion is a correct statement.
Reason is a false statement because F will be attractive if the two currents I2 and I2 will be in the same directions and repulsive if in opposite directions.
is the generalization ofRelative permeability,
μr is a dimensionless quantity.
Consider the volume current density distribution in cylindrical co-ordinates as
Where a and b are inner and outer radii of the cylinder as shown in figure below
Now, consider the value of magnetic field intensity in various regions I, II and III respectively obtained as:
Which of the above found values of H are correct for the respective regions?
- For region-I (0 < r < a), J (r, ϕ, z) = 0
Using Ampere’s law, we have
or , H·2πr = 0 or H = 0 - For region - II
Again,
or,
- For region - III (b < r < ∞), J = 0
Again,
Assertion (A): It is not possible to have isolated magnetic charges.
Reason (R): The magnetic flux lines always close upon themselves.
Since, magnetic flux lines always close upon themselves therefore it is not possible to have isolated magnetic charges (or poles).
Match List-l with List-lI and select the correct answer using the codes given below the fists:
List-l
A. Gauss’s law for magnetostatic fields
B. Gauss’s law for electrostatic fields
C. Conservativeness of electrostatic fields
D. Ampere's law
List-lI
Codes:
A B C D
(a) 5 4 1 2
(b) 3 1 4 5
(c) 3 4 1 5
(d) 5 1 4 2
The magnetic vector potential is given by
The total magnetic flux crossing the surface ϕ = π/2 , 1 ≤ ρ ≤ 2 m , 0 ≤ z ≤ 5 m is
The total magnetic flux crossing the surface
ϕ = π/2 , 1 ≤ ρ ≤ 2 m , 0 ≤ z ≤ 5 m is given as:
= 3.75 Wb
Which of the following is not a source of magnetostatic fields?
An accelerated charge will produce both time varying electric and magnetic field called electromagnetic field.
Consider the following statements associated with the characteristics of static magnetic field:
1. It is solenoidal.
2. Magnetic flux lines are not closed in certain cases.
3. The total number of flux lines entering a given region is equal to the total number of flux lines leaving the region.
4. It is conservative.
Which of the above statements is/are not correct?
- Static magnetic field is non-conservative unlike static electric field. Hence, statement-4 is not correct.
- Magnetic flux lines are always closed. Hence, statement-2 is not correct.
- Statement 1 and 3 are correct.
What are the units for the product of two values whose respective units are Henrys and Amperes?
The Henry, the unit for mutual inductance is equivalent to V-sec/Ampere.
So, H x Ampere = Volt-sec = V-s
What are the possible dimensions for a rectangular coil that has a magnetic flux of 9.5 webers when in a magnetic field of strength 19 Tesla at an angle of 60° from the perpendicular to the plane of the coil?
Magnetic flux φB = BA cosθ
or, 
Hence, the area of the rectangular coil should be 1 m2. Only option (d) is matching the answer i.e. 250 cm x 40 cm
= 10000 cm2 = 1 m2.
What is the change in magnetic fiux in a coil of area 5 m2 as its orientation relative to the perpendicular of a uniform 3.0 T magnetic field changes from 45° to 90°?
Flux ϕ = B A cosθ
At θ = 45°, ϕ1= 3 x 5 x cos 45° = 11 Wb
At θ = 90°, ϕ2 = 3 x 5 x cos 90° = 0 Wb
∴ Change in flux = ϕ2 - ϕ1 = -11 Wb
is solenoidal, which of these is true?
(Non-existence of monopole)
If 
, the value of 
around the closed circular quadrant shown in the given figure is
is based onGiven a vector field 
in cylindrical coordinates. For the contour as shown below, 
is
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