XII Physics Electromagnetism Online Test Mdcat-2024

1. When current in a straight wire is flowing towards north, a compass needle placed
near it points in E-W direction. What happens when the direction of current is
reversed?

2. Four particles enter in a uniform magnetic field perpendicularly with same speed.
Which particle has largest radius?

3. When charge particle enters perpendicular to magnetic field, the path followed by it
is:

4. A long straight wire is in the plane of a rectangular conducting loop. The straight
wire carries a constant current i, as shown. While the wire is being moved toward
the rectangle the current in the rectangle is:

5. A proton is moving along the axis of a solenoid carrying a current as shown in figure.
The magnetic force on proton will be:

6. The figure shows a uniform magnetic field B directed to the left and a wire carrying a
current Into the page. The magnetic force acting on the wire is:

7. A 2-T uniform magnetic field makes an angle of 30◦ with the z axis. The magnetic flux
through a 3 m² portion of the xy plane is:

8. A magnetic field Can't:

9. Normal street transformer are efficient upto:

10. The frequency of AC main in Pakistan is:

11. The loss of energy over each A.C cycle magnetization and demagnetization of
transformer, is called:

12. Magnitude of induced EMF is determined by:

13. The primary winding of transformer has 500 turns whereas its secondary has 5000
turns. The primary is connected to an ac supply of 20 V, 50 Hz. The secondary will
have an output of:

14. The ratio of secondary to the primary turns in a transformer is 3 : 2. If the power
output be P, then the input power neglecting all loses must be equal to:

15. A transformer is based on the principle of :

16. The current in a coil changes from 4 ampere to zero in 0.1 s. If the average e.m.f.
induced is 100 volt, what is the self inductance of the coil

17. Lenz law is used to define:

18. A metallic ring is attached with the wall of a room. When the north pole of a magnet
is brought near to it, the induced current in the ring will be:

19. Magnetic field due to 0.1 A current flowing through a circular coil of radius 0.1 m and 1000 turns at the centre of the coil is:

20. Two long straight wires are set parallel to each other. Each carries a current (i) in the same direction and the separation between them is 2r. Magnetic field intensity at a point between (midway) them:

21. Field at the centre of a circular coil of radius r, through which a current I flows is:

22. To construct a step-down transformer:

23. SI unit of inductance is:

24. Motional EMF can be produced with:

25. Lenz law is law for explaining:

26. Slip rings instead of split rings are used in:

27. The core of a transformer is laminated so that:

28. If the angular frequency of a dynamo armature is doubled, then the induced EMF will become:

29. Quantity of the following remains unchanged in a transformer is:

30. A step-up transformer is used on a 120V line to provide a potential difference of 2400V. If the primary coil has 75 turns, the number of turns in the secondary coil is:

31. A transformer is designed to convert the voltage from 240 V A.C mains to 12 V, and has 4000 turns on its primary coil. If it is 100% efficient, and the current in the secondary coil was 0.4 A then the current in the primary coil should be:

32. 1 weber is the same as:

33. Induced EMF in the coil depends upon:

34. In a transformer, the number of turns of primary coil and secondary coil are 5 and 4 respectively. If 220 V is applied on the primary coil, then the ratio of primary current to the secondary current is:

35. A transformer is used to light 140-watt 24-volt lamp from 240 volt AC mains; the current in the main cable is 0.7 amp. The efficiency of the transformer is:

36. A coil having 500 square loops, each of side 10 cm, is placed normal to a magnetic field which increases at the rate of 1.0T/s. The induced EMF in volts is:

37. Find the correct statement:

38. If magnetic field vector is B = i + 5j + 2k and area vector is ΔA = 6i +2j - 2k then flux is:

39. charge particle is projected into a region such that it enters perpendicularly to a uniform B pointed into the paper. If charge particle enters with a K.E of 2ev then:

40. proton (or charged particle) moving with velocity v is acted upon by electric field E and magnetic field B. The proton will move undeflected if:

41. Magnetism phenomenon is related to:

42. The charge to mass ratio of an electron is:

43. Direction of magnetic flux can be:

44. A charge of 1C is moving in a magnetic field of 0.5 tesla with a velocity of 10m/sec perpendicular to the field. Force experienced is:

45. Which of the following relationship is correct:

46. An electron is moving north in a region where the magnetic field is south. The magnetic force exerted on the electron is:

47. If charge to mass ratio of some particle is increased, then its frequency of cyclotron will:

48. If a particle is moving in a region of both electric & magnetic fields then the total force acting on it is:

49. An electron moving east is acted on by a magnetic field in the north direction. The force on the electron is:

50. A proton and a particle enter with the same velocity at 90° in a uniform magnetic field. Ratio of the radius of their paths will be: