1. The flux-density at a distance of 0.1 m from a long straight wire, carrying a current of 200 A is

- 5 x 10
^{-4}Wb/m^{2} - 4 x 10
^{-4}Wb/m^{2} - 3 x 10
^{-4}Wb/m^{2} - 2 x 10
^{-4}Wb/m^{2}

2. An iron rod of 10^{-3} m^{3} volume and relative permeability of 1150 is placed inside a long solenoid wound with 5 turns/cm. If a current of 0.5 A is allowed to pass through the solenoid, the magnetic moment of the rod is

- 2.87 x 10
^{4}A-m^{2} - 28.7 x 10
^{3}A-m^{2} - 2.87 x 10
^{2}A-m^{2} - 28.7 x 10
^{2}A-m^{2}

3. The magnetic susceptibility of aluminium is 2.1 x 10^{-5}. The permeability and relative permeability are, respectively

- 12.6 x 10
^{-7}and 1.0021 - 1.26 x 10
^{-7}and 1.0021 - 12.6 x 10
^{-7}and 1.000021 - 1.26 x 10
^{-7}and 1.000021

4. The magnitude of magnetic field strength H is independent of

- current only
- distance only
- permeability of the medium only
- both current and distance

5. A conductor of length 100 cm moves at right angle to a uniform field flux density of 1.5 Wb/m with a velocity of 50 m/s. The e.m.f. induced in conductor will be

- 150 V
- 75 V
- 50 V
- 37.5 V

6. Two conductors of a transmission line carry equal current I in opposite directions. The force on each conductor is proportional to

- I
- I
^{2} - the distance between the conductors
- I
^{3}

7. The law which states that the line integral of the magnetic field around a closed curve is equal to the free current through a surface, is

- Tellegen’s theorem
- Gauss’ law
- Ampere’s law
- Coulomb’s law

8. If the current density inside a straight conductor is uniform over its cross-section, the flux density variation inside the conductor at different distances from its centre is

- linear
- square of the distance
- inverse of the distance
- exponential

9. For electromechanical energy conversion, a magnetic field is employed as the medium rather than electric field because

- the stored energy density for practicable field strength is low in the electric field
- the electric field presents insulation problem
- the specific magnetic loss is more than the specific dielectric loss
- None of the above

10. A magnetic ring has a mean circumference of 20 cm and a cross-section of 20 cm^{2} and has 800 numbers of turns of wire. When the exciting current is 5 A, the flux is 2 mWb. The relative permeability of iron is nearly

- 3.98
- 398
- 39.8
- 0.398

11. Consider the following statements:

A current I flows through a circular coil of one turn of radius R in the counter-clockwise direction.

- The magnetic field at the center is inversely proportional to R.
- The magnetic moment of the coil is directly proportional to R
^{2}. - The magnetic field at its center is directly proportional to R
^{2}.

Which of the above statements is/are correct?

- i and ii
- i only
- ii and iii
- iii only

12. Along straight wire carries a current I = 10 A, the magnetic field at a distance of 1.59 m is

- 0.1 Am
^{-1} - 1 Am
^{-1} - 10 Am
^{-1} - 100 Am
^{-1}

13. If the magnetic flux through each turn of the coil consisting of 200 turns is (t^{2} – 3t) milli-Webers, where t is in seconds, then the induced emf in the coil at t= 4 sec is

- -1 V
- 1 V
- -0.1 V
- 0.1 V

14. The unit of magnetic flux density is

- gauss
- tesla
- bohr
- weber/sec

15. How much current must flow in a loop of radius 1 m to produce a magnetic field 1 mAm^{-1}?

- 1.5 mA
- 1.0 mA
- 2.5 mA
- 2.0 mA

16. A long straight wire carries a current I = 1A. At what distance is the magnetic field 1 Am^{-1}?

- 1.59 m
- 0.159 m
- 0.00159 m
- 0.0159 m

17. A long straight wire carries a current I = 10 A. At what distance is the magnetic field H= 1 Am^{-1}?

- 1.39 m
- 1.19 m
- 1.59 m
- 1.79 m

18. If a very flexible wire is laid out in the shape of a hairpin with its two ends secured, what shape will the wire tend to assume if a current is passed through it?

- Parabolic
- Straight line
- Circle
- Ellipse