Magnetism — Set 2
Physics · चुंबकत्व · Questions 11–20 of 50
Paramagnetic materials are generally?
Correct Answer: B. Weakly attracted by a magnet
Paramagnetic materials are weakly attracted to a magnetic field. Their atoms tend to align slightly with the applied field. The effect is usually much weaker than in ferromagnets.
Ferromagnetic materials are generally?
Correct Answer: B. Strongly attracted by a magnet
Ferromagnetic materials are strongly attracted because they can be strongly magnetized. They contain domains that can align in the same direction. Iron, cobalt, and nickel are common ferromagnets.
Curie temperature is the temperature above which a ferromagnetic material generally becomes?
Correct Answer: B. Paramagnetic
Above the Curie temperature, ferromagnetic order breaks down and the material becomes paramagnetic. Thermal motion disturbs the domain alignment. Below this temperature, strong magnetism can appear again.
Soft iron is preferred for making electromagnet cores mainly because it has?
Correct Answer: C. Low retentivity and high permeability
Soft iron becomes strongly magnetized and also loses magnetism easily, so it suits electromagnets. High permeability helps it produce a strong field for a given current. Low retentivity reduces unwanted magnetism after switching off.
Steel is often used for permanent magnets mainly because it has?
Correct Answer: A. High retentivity
Steel is chosen because it can retain magnetism well, which is high retentivity. This helps a permanent magnet keep its strength for a long time. Hard magnetic materials usually also have higher coercivity.
Hysteresis loss in a magnetic material is related to the?
Correct Answer: D. Area of the B-H loop
Hysteresis loss per cycle is represented by the area enclosed by the B-H loop. A larger loop means more energy is lost as heat each cycle. This is important in transformer and motor core selection.
The right-hand thumb rule is used to find the direction of?
Correct Answer: D. Magnetic field around a current-carrying conductor
The right-hand thumb rule gives the magnetic field direction around a straight current-carrying wire. Point the right thumb along the current and the curled fingers show the field direction. The field forms concentric circles around the wire.
Fleming’s left-hand rule is mainly used to predict the direction of?
Correct Answer: D. Force on a current-carrying conductor in a magnetic field
Fleming’s left-hand rule gives the direction of force on a current-carrying conductor in a magnetic field. It relates the directions of field, current, and force. This rule is widely used for electric motors.
Fleming’s right-hand rule is mainly associated with finding the direction of?
Correct Answer: A. Induced current in electromagnetic induction
Fleming’s right-hand rule is used for electromagnetic induction to find induced current direction. It relates the motion of the conductor, magnetic field, and induced current. This rule is commonly linked with generators.
The magnetic force on a moving charge in a magnetic field is described by?
Correct Answer: C. F = q(v × B)
A moving charge in a magnetic field experiences a force given by q times v cross B. The force is perpendicular to both velocity and magnetic field direction. If the charge is at rest, this magnetic force becomes zero.