1. What is the Biot-Savart law and how is it applied to a current-carrying circular loop?
Answer: The Biot-Savart law states that the magnetic field produced by a current-carrying conductor is directly proportional to the current, the length of the conductor, and the sine of the angle between the position vector and the direction of the current. It’s applied to a current-carrying circular loop to calculate the magnetic field at any point on the loop’s axis.
2. Explain Ampere’s law and its applications to infinitely long current-carrying straight wire and a solenoid.
Answer: Ampere’s law states that the magnetic field around a current-carrying conductor is directly proportional to the current passing through the conductor and inversely proportional to the distance from the conductor. It’s applied to infinitely long current-carrying straight wires and solenoids to calculate the magnetic field strength at various points.
3. What is the force on a moving charge in a uniform magnetic field and how is it calculated?
Answer: The force on a moving charge in a uniform magnetic field is given by the equation F = qvBsinθ, where F is the force, q is the charge, v is the velocity of the charge, B is the magnetic field strength, and θ is the angle between the velocity vector and the magnetic field vector.
4. Describe the force on a current-carrying conductor in a uniform magnetic field.
Answer: A current-carrying conductor in a uniform magnetic field experiences a force perpendicular to both the direction of the current and the direction of the magnetic field. The magnitude of the force is given by F = ILBsinθ, where I is the current, L is the length of the conductor, B is the magnetic field strength, and θ is the angle between the current direction and the magnetic field direction.
5. Define the force between two parallel current-carrying conductors and define Ampere.
Answer: The force between two parallel current-carrying conductors is given by the equation F = (μ₀I₁I₂L)/(2πd), where μ₀ is the permeability of free space, I₁ and I₂ are the currents in the conductors, L is the length of the conductors, and d is the distance between them. Ampere is the SI unit of electric current, defined as the amount of charge passing through a given point in a circuit per unit time.
6. Explain the torque experienced by a current loop in a uniform magnetic field.
Answer: When a current loop is placed in a uniform magnetic field, it experiences a torque that tends to align the loop with the magnetic field. The magnitude of the torque is given by τ = μBsinθ, where μ is the magnetic dipole moment of the loop, B is the magnetic field strength, and θ is the angle between the magnetic dipole moment and the magnetic field.
7. What is a moving coil galvanometer, and how is it converted to an ammeter and voltmeter?
Answer: A moving coil galvanometer is a device used to detect and measure small electric currents. It can be converted into an ammeter by connecting a low resistance (shunt) in parallel with the galvanometer coil to measure large currents, and into a voltmeter by connecting a high resistance (multiplier) in series with the galvanometer coil to measure large voltages.
8. Explain the concept of a current loop as a magnetic dipole and its magnetic dipole moment.
Answer: A current loop generates a magnetic field similar to that of a magnetic dipole. The magnetic dipole moment (μ) of the loop is given by the product of the current (I) and the area (A) of the loop, μ = IA. The direction of the magnetic dipole moment is perpendicular to the plane of the loop, following the right-hand rule.
9. How is a bar magnet considered as an equivalent solenoid?
Answer: A bar magnet can be considered as an equivalent solenoid because both have similar magnetic field patterns. The magnetic field lines outside the magnet resemble those around a solenoid, while inside the magnet, the field lines run from the north pole to the south pole, similar to the magnetic field inside a solenoid.
10. Explain magnetic field lines and their characteristics.
Answer: Magnetic field lines are imaginary lines used to represent the direction and strength of a magnetic field. They are continuous loops that emerge from the north pole of a magnet and enter the south pole. The density of magnetic field lines indicates the strength of the magnetic field, with more lines per unit area indicating stronger fields.
11. What is the magnetic field due to a magnetic dipole (bar magnet) along its axis and perpendicular to its axis?
Answer: Along the axis of a magnetic dipole (bar magnet), the magnetic field follows the pattern of a dipole field, with the field lines emerging from the north pole and entering the south pole. Perpendicular to the axis, the magnetic field forms circular loops around the magnet.
12. Describe the torque experienced by a magnetic dipole in a uniform magnetic field.
Answer: A magnetic dipole placed in a uniform magnetic field experiences a torque that tends to align it with the field direction. The magnitude of the torque is given by τ = μBsinθ, where μ is the magnetic dipole moment, B is the magnetic field strength, and θ is the angle between the dipole moment and the field direction.
13. Differentiate between para-, dia-, and ferromagnetic substances with examples.
Answer: Paramagnetic substances have unpaired electrons and are weakly attracted to magnetic fields (e.g., aluminum). Diamagnetic substances have no unpaired electrons and are weakly repelled by magnetic fields (e.g., copper). Ferromagnetic substances have domains of aligned magnetic moments and are strongly attracted to magnetic fields (e.g., iron).
14. Explain the effect of temperature on magnetic properties.
Answer: Temperature affects the magnetic properties of materials by influencing the alignment of magnetic moments. In ferromagnetic materials, heating above the Curie temperature disrupts the alignment, causing them to lose their magnetic properties. In paramagnetic and diamagnetic materials, temperature changes may alter the degree of magnetization but usually have less pronounced effects.
15. Discuss the application of the Biot-Savart law to a current-carrying circular loop.
Answer: The Biot-Savart law is used to calculate the magnetic field at any point around a current-carrying circular loop. By integrating the contributions of infinitesimal current elements along the loop, the total magnetic field strength and direction at a specific point can be determined.
16. How is Ampere’s law applied to calculate the magnetic field produced by an infinitely long current-carrying straight wire?
Answer: Ampere’s law states that the magnetic field around an infinitely long current-carrying straight wire is circular and perpendicular to the wire. By applying Ampere’s law, one can calculate the magnetic field strength at various distances from the wire by considering a circular path around the wire and integrating the current enclosed by that path.
17. Explain the force between two parallel current-carrying conductors and its calculation.
Answer: The force between two parallel current-carrying conductors is due to the interaction of their magnetic fields. The force per unit length between two parallel conductors is given by the equation F = (μ₀I₁I₂L)/(2πd), where μ₀ is the permeability of free space, I₁ and I₂ are the currents in the conductors, L is the length of the conductors, and d is the distance between them.
18. Describe the operation of a moving coil galvanometer and its sensitivity.
Answer: A moving coil galvanometer consists of a coil suspended in a magnetic field. When current flows through the coil, it experiences a torque that causes it to rotate. The sensitivity of the galvanometer refers to its ability to detect small currents, which is determined by factors such as the number of turns in the coil and the strength of the magnetic field.
19. How can a moving coil galvanometer be converted into an ammeter and voltmeter?
Answer: A moving coil galvanometer can be converted into an ammeter by connecting a low resistance (shunt) in parallel with the galvanometer coil to measure large currents. To convert it into a voltmeter, a high resistance (multiplier) is connected in series with the galvanometer coil to measure large voltages.
20. Discuss the concept of a current loop as a magnetic dipole and its significance.
Answer: A current loop generates a magnetic field similar to that of a magnetic dipole. This concept is significant in understanding the behavior of magnetic materials and electromagnetic devices. The magnetic dipole moment of the loop determines its interaction with external magnetic fields and its ability to produce torque when placed in a magnetic field, which has practical applications in devices such as motors and generators.