MAGNETIC EFFECT OF CURRENT MCQ

Q.1. Biot-Savart law indicates that the moving electrons (velocity v) produce a magnetic field B such that

• (a) B ⊥ v.

• (b) B || v.

• (c) it obeys inverse cube law.

• (d) it is along the line joining the electron and point of observation.

Q.2. Two charged particles traverse identical helical paths in a completely opposite sense in a uniform magnetic field B = B0k.

• (a) They have equal z-components of momenta.

• (b) They must have equal charges.

• (c) They necessarily represent a particle- antiparticle pair.

• (d) The charge to mass ratio satisfy: (e/m)1+(e/m)2=0

Q.3. A circular coil of radius 4 cm and of 20 turns carries a current of 3 amperes. It is placed in a magnetic field of intensity of 0.5 weber/m². The magnetic dipole moment of the coil is

• (a) 0.15 ampere-m²

• (b) 0.3 ampere-m²

• (c) 0.45 ampere-m²

• (d) 0.6 ampere-m²

Q.4. The conversion of a moving coil galvanometer into a voltmeter is done by

• (a) introducing a resistance of large value in series.

• (b) introducing a resistance of small value in parallel.

• (c) introducing a resistance of large value in parallel.

• (d) introducing a resistance of small value in series.

Q.5. An electron is projected with uniform velocity along the axis of a current carrying long solenoid. Which of the following is true?

• (a) The electron will be accelerated along the axis.

• (b) The electron path will be circular about the axis.

• (c) The electron will experience a force at 45° to the axis and hence execute a helical path.

• (d) The electron will continue to move with uniform velocity along the axis of the solenoid.

Q.6. In a cyclotron, a charged particle

• (a) undergoes acceleration all the time.

• (b) speeds up between the dees because of the magnetic field.

• (c) speeds up in a dee.

• (d) slows down within a dee and speeds up between dees.

Q.7. If a charged particle moves through a magnetic field perpendicular to it

• (a) both momentum and energy of particle change.

• (b) momentum as well as energy are constant.

• (c) energy is constant but momentum changes.

• (d) momentum is constant but energy changes.

Q.8. A rectangular loop carrying a current i is situated near a long straight wire such that the wire is parallel to the one of the sides of the loop and is in the plane of the loop. If a steady current I is established in wire as shown in figure, the loop will

• (a) rotate about an axis parallel to the wire.

• (b) move away from the wire or towards right.

• (c) move towards the wire.

• (d) remain stationary.

Q.9. A cubical region of space is filled with some uniform electric and magnetic fields. An electron enters the cube across one of its faces with velocity v and a positron enters via opposite face with velocity -v. At this instant,

• (a) the electric forces on both the particles cause identical accelerations.

• (b) the magnetic forces on both the particles cause equal accelerations.

• (c) Only electron gains or looses energy.

• (d) the motion of the centre of mass (CM) is determined by E alone.

Q.10. The maximum current that can be measured by a galvanometer of resistance 40 Ω is 10 mA. It is converted into voltmeter that can read upto 50 V. The resistance to be connected in the series with the galvanometer is

• (a) 2010 Ω

• (b) 4050 Ω

• (c) 5040 Ω

• (d) 4960 Ω