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WorksheetsMAGNETIC EFFECT OF CURRENT MCQ
Total questions: 20
Worksheet time: 20mins
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
Q.11. The strength of magnetic field at the centre of circular coil is
a
b
c
d
Q.12. A current carrying closed loop of an irregular shape lying in more than one plane when placed in uniform magnetic field, the force acting on it
(a) will be more in the plane where its larger position is covered.
(b) is zero.
(c) is infinite.
(d) may or may not be zero.
Q.13. If the beams of electrons and protons move parallel to each other in the same direction, then they
(a) attract each other.
(b) repel each other.
(c) no relation.
(d) neither attract nor repel.
Q.14. A conducting circular loop of radius r carries a constant current i. It is placed in a uniform magnetic field B, such that B is perpendicular to the plane of the loop. The magnetic force acting on the loop is
(a) irB
(b) 2πriB
(c) zero
(d) πriB
Q.15. The gyro-magnetic ratio of an electron in an H-atom, according to Bohr model, is
(a) independent of which orbit it is in.
(b) neutral
(c) positive
(d) increases with the quantum number n.
Q.16. An electron is projected along the axis of a circular conductor carrying the same current. Electron will experience
(а) a force along the axis.
(b) a force perpendicular to the axis.
(c) a force at an angle of 45° with axis.
(d) no force experienced.
Q.17. Three long, straight parallel wires, carrying current are arranged as shown in the figure. The force experienced by a 25 cm length of wire C is
(a) 10^-3 N
(b) 2.5 × 10^-3 N
(c) zero
(d) 1.5 × 10^3 N
Q.18. What is the net force on the rectangular coil?
(a) 25 × 10^-7 N towards wire.
(b) 25 × 10^-7 N away from wire.
(c) 35 × 10^-7 N towards wire.
(d) 35 × 10^-7 N away from wire.
Q.19. In a circular coil of radius r, the magnetic field at the centre is proportional to
(a) r²
(b) r
(c) 1/r
(d) 1/r²
Q.20. A positive charge enters in a magnetic field and travels parallel to but opposite the field. If experiences
(a) an upward force.
(b) a downward force.
(c) an accelerated force.
(d) no force.
