\Section 7 part 3 - Magnetic fields and EM Induction Flashcards
Define a magnetic field
A force field surrounding a magnet or current carrying wire which acts on any other magnet or current carrying wire placed in the field
Where is the magnetic field of a bar magnet strongest?
At the ends (poles)
What are magnetic field lines?
Lines of force
What do the arrows on magnetic field lines represent?
The direction a small free north pole would move if placed in the field
Can field lines cross?
No, they show the resultant force
What is a neutral point, and how are they created?
A point where no force is experienced, and created when like poles are near to each other
What do current carrying wires produce?
A magnetic field
Define motor effect
A current carrying wire when placed at a non-zero angle to the lines of force of an external magnetic field feels a force due to a field. This effect is the motor effect
Which direction does the force act in the motor effect?
Perpendicular to the current and lines of force
What does the force experienced by an object in a magnetic field depend on?
The current, strength of magnetic field, length of wire, angle between lines of force and current direction
When is the force experienced by a wire in a magnetic field strongest and weakest?
The force is max when the wire is at right angles to the magnetic field
The force is 0 when the wire is parallel to the magnetic field
Define magnetic flux density
The strength of the magnetic field - the force per unit length per unit current-carrying conductor at right angles to the magnetic field lines
State the components and the conditions for the equation F=BIL
F = Force, N B = Magnetic flux density, T I = Current, A L = Length, m B and I must be at right angles for the equation to apply
What is the equation for torque on a coil at an angle to the magnetic field lines?
T = BIANcostheta, or BILdN
State the components for the equation T = BIANcostheta
T = Torque, Nm B = Magnetic field density, T A = Area, M^2 N = Number of turns in wire costheta = Angle between coil and field lines
Why do electron beams move in a circular path
The direction of the force on each electron is perpendicular to the direction of motion of the electron
Which direction do stationary charges in a magnetic field experience a force relative to?
They don’t experience a force
What is the equation for Hall voltage?
V = Bvd
Can magnetic fields do work on charged particles?
No, as the force is always perpendicular to the velocity. The direction of motion is changed by the force, but not the motion
How much does the magnetic field change the kinetic energy of a charged particle?
It cannot
What is the equation for the radius of a charged particle path?
r = mv/BQ
Define the motor effect
A current carrying wire with its associated magnetic field will experience a motor effect if placed at a non-zero angle in a magnetic field