Magnetic Fields Flashcards
What is a magnetic field?
A magnetic field is the force per unit current per unit length placed at a right angle to an external magnetic field.
What are the two main sources of a magnetic field?
Current-carrying conductors and permanent magnets.
How do magnetic field lines behave around a permanent magnet?
Magnetic field lines emerge from the north pole and enter the south pole.
What does the tangent to a magnetic field line represent?
It shows the direction of force on a ‘free’ magnetic north pole at that point.
Where is the magnetic field strongest?
Where the field lines are closest together.
How can the strength of a magnetic field in a solenoid be increased?
By increasing the current, increasing the number of turns per unit length, or using a soft-iron core.
What does the Right-Hand Grip Rule state for a straight conductor?
The thumb points in the direction of the current, and the curled fingers show the direction of magnetic field lines.
How do the field lines behave around a long, straight conductor?
They form concentric circles centered at the conductor, with spacing increasing as distance increases.
How does the magnetic field of a solenoid compare to that of a bar magnet?
The solenoid produces a similar field pattern to a bar magnet, with parallel field lines inside indicating a uniform field.
How do you determine the poles of a solenoid?
Use the Right-Hand Grip Rule, where the fingers show current direction and the thumb points to the north pole.
How does a ferrous core affect a solenoid’s magnetic field?
It increases the field strength by about 1000 times due to its higher permeability and its own magnetization.
What is Fleming’s Left-Hand Rule?
Thumb = Force, Index Finger = Magnetic Field, Middle Finger = Current.
How can the force on a current-carrying conductor in a magnetic field be increased?
By increasing the current or using a stronger magnet.
How do forces act between two parallel current-carrying wires?
If currents are in the same direction, the wires attract; if opposite, they repel.
What is the formula for magnetic flux?
Φ = BA (Magnetic flux = Magnetic flux density × Perpendicular area).
What is the formula for force on a conductor in a magnetic field?
F = BIL sin(θ).
When is the force on a current-carrying wire in a magnetic field zero?
When the wire is parallel to the field lines (θ = 0°).
What happens when the wire is perpendicular to the magnetic field?
The force is at its maximum (F = BIL).
How can a current balance be used to measure flux density?
By equating gravitational force (mg) to magnetic force (BIL).
What is the unit of magnetic flux density?
Tesla (T), where 1T = 1 N A⁻¹ m⁻¹.
What is the formula for force on a moving charge in a magnetic field?
F = BQv sin(θ).
What happens if a charged particle moves parallel to a magnetic field?
No force acts on it (F = 0).
How does a charged particle move if it enters a magnetic field at a right angle?
It follows a circular path due to the perpendicular force.
How does mass affect the radius of a charged particle’s circular motion in a magnetic field?
A heavier particle moves in a larger circle (r ∝ m).
