Physics Self-Test - Page 9
61- If the number of atoms in the domain in ferromagnetic iron, in the form of a cube of side length 1μm, is 8.65 × 10¹° atoms and dipole moment of each iron atom is 9.27 × 10»²&#Values; Am², what is the maximum Magnetization of the domain?
- a) 6 × 105 A/m
- b) 7 × 105 A/m
- c) 8 × 105 A/m
- d) 9 × 105 A/m
61- Magnetism originates due to rotational motion of charged particles.
Explanation: Atomic magnetism is primarily driven by the orbital rotation and intrinsic spin states of negatively charged electrons.
62- In which of the following magnetic moment is zero?
- a) Dia-magnetic material
- b) Paramagnetic material
- c) Ferromagnetic material
- d) Ferrimagnetic material
Explanation: In diamagnetic substances, all electron spins are fully paired within their shells, resulting in a zero net permanent magnetic dipole moment in the absence of an external field.
63- When does a diamagnetic material become normal material?
- a) At critical temperature
- b) Above critical temperature
- c) Never
- d) Below critical temperature
63- Magnetic field lines form ____________ loops from pole to pole.
- a) Open
- b) Closed
- c) Branched
- d) Either closed or branched
Explanation: Unlike electric field lines that start and stop on individual isolated static charges, magnetic field lines always maintain unbroken, continuous closed loops due to the absence of isolated magnetic monopoles.
64- Inside the magnet, field lines travel from?
- a) North to south
- b) South to north
- c) West to east
- d) East to west
Explanation: To form continuous loops, magnetic field lines emerge from the North pole and enter the South pole *externally*, then travel from South back to North *internally* inside the magnet core.
64- Lines of magnetic flux which are parallel and in the same direction ____________ each other.
- a) Attract
- b) Repel
- c) Intersect
- d) Cancel
66- Which, among the following qualities, is not affected by the magnetic field?
- a) Moving charge
- b) Change in magnetic flux
- c) Current flowing in a conductor
- d) Stationary charge
Explanation: The Lorentz magnetic force formula is given by $F = q(v \times B)$. If a charge is stationary ($v = 0$), the cross product becomes zero, meaning it experiences no deflection force.
67- When a charged particle moves at right angles to the magnetic field, the variable quantity is?
- a) Momentum
- b) Speed
- c) Energy
- d) Moment of inertia
Explanation: The magnetic deflection force acts perpendicularly to the velocity vector, changing its path trajectory (direction) while leaving kinetic energy and speed constant. Since velocity direction shifts, **momentum** ($p = m \cdot v$) alters over time.