NTSE SAT Physics Emi MCQs

Question: A wire carrying a current of 5 A is placed perpendicular to a magnetic induction of 2T. The force on each centimeter of the wire is :

• a) 0.1 N
• b) 10 N
• c) 100 N
• d) 1 N

Answer: 0.1 N

Question: The frequency of alternating current (A.C.) in India is :

• a) 50 Hz
• b) 100 Hz
• c) 220 Hz
• d) 440 Hz

Answer: 50 Hz

Question: Induced electromotive force in a coil does not depend on :

• a) Number of turns in the coil
• b) Intensity of the magnetic field
• c) Relative speed between coil and the magnet
• d) Resistance of the coil

Answer: Resistance of the coil

Question: A transformer steps up an a.c. supply from 220 to 2200 V. If the secondary coil of the transformer has 2000 turns, the number of turns is its primary coil will be :

• a) 200
• b) 100
• c) 50
• d) 20

Answer: 200

Question: A step down transformer reduces 220V to 11V. The primary draws 5 A current and secondary supplies 90A. Efficiency of the transformer will be :

• a) 4.4%
• b) 20%
• c) 33%
• d) 90%

Answer: 90%

Question: A transformer is used :

• a) To transform electric energy into mechanical energy
• b) To obtain suitable dc voltage
• c) To transform as into dc
• d) To obtain suitable as voltage

Answer: To obtain suitable as voltage

Question: What is increased in a step down transformer ?

• a) Voltage
• b) Current
• c) Wattage
• d) None of these

Answer: Current

Question: In circular coil current is flowing in anticlockwise direction, then the direction of magnetic field produced at the center of coil, will be :

• a) In the plane of coil
• b) Perpendicular to the plane of coil
• c) In the direction of current
• d) Parallel to any diameter

Answer: Perpendicular to the plane of coil

Question: A current passes through a coil in the anticlockwise direction. The magnetic field at a point on the axis of the coil is :

• a) Parallel to the plane of the coil
• b) Perpendicular to the axis of the coil
• c) Along the axis towards the center of the coil
• d) Along the axis away from the center of the coil

Answer: Along the axis away from the center of the coil

Question: Current is induced in a coil by electromagnetic induction when :

• a) Only the coil moves in a magnetic field.
• b) Only the magnet moves towards the coil.
• c) Coil and the magnet move with respect to each other.
• d) None of the above

Answer: Coil and the magnet move with respect to each other.

Question: The transformer voltage induced in the secondary coil of a transformer is mainly due to :

• a) The iron core of the transformer
• b) The vibration of the primary coil
• c) A varying induced electric field
• d) A varying induced magnetic field

Answer: A varying induced magnetic field

Question: The frequency of alternating current (A.C.) in India is :

• a) 50 Hz
• b) 100 Hz
• c) 220 Hz
• d) 440 Hz

Answer: 50 Hz

Question: A wire carrying a current of 5 A is placed perpendicular to a magnetic induction of 2T. The force on each centimeter of the wire is :

• a) 0.1 N
• b) 10 N
• c) 100 N
• d) 1 N

Answer: 0.1 N

Question: What is increased in a step down transformer ?

• a) Voltage
• b) Current
• c) Wattage
• d) None of these

Answer: Current

Question: The transformer voltage induced in the secondary coil of a transformer is mainly due to :

• a) The iron core of the transformer
• b) The vibration of the primary coil
• c) A varying induced electric field
• d) A varying induced magnetic field

Answer: A varying induced magnetic field