Magnetic Fields Flashcards
What is the symbol used to indicate that the magnetic field of travelling into the screen ?
A cross / x
What is the symbol to indicate a magnetic field coming out of the screen ?
A dot
What will the size of the source be when the conductor is parallel to the field ?
0 as the the conductor would have to be perpendicular to the magnetic field to experience a force.
How can you convert rms current into amps ?
Current = I rms * root 2
If an alternating current is passed through a wire why would the wire vibrate vertically?
Using lemmings left hand rule we are able to understand that the force is perpendicular to the field and current however when I is reversed f acts in the opposite direction. Continuous reversal of I means constant change in direction so f keeps switching / vibrating vertically.
What are two situations in which a charged particle will experience no magnetic force within a field ?
Charged particles at rest (not moving relative to the field or travels in a motion parallel to the field (flux )
Why is it not possible for the magnetic field to alter the speed of a proton while it is in one of the d shaped regions ?
F is perpendicular to the velocity so there is no component of force in the direction of motion (no work is done and kinetic energy and the velocity remain constant )
What is a magnetic field ?
A regional in which a magnetic materials or a magnet experiences a magnetic force ( can be repulsive or attractive )
What is the direction of the magnetic field with a current carrying conductor?
Using the right hand rule :
thumb indicating the direction of the current
The fingers wrapped indicating the magnetic field
What is the motor effect caused by ?
A current carrying conducting interacting with the magnetic field of a permanent magnet resulting in the conductor to experience a force
When is the force a maximum in the motor effect ?
When the current is perpendicular to the field
When is the force zero in the motor effect ?
When the current is parallel to the magnetic field
What does the thumb represent in Flemings left hand rule ?
The direction of the force
What is the index finger used to represent in the Flemings left hand rule ?
The magnetic field ( north to south )
What does the middle finger represent in Flemings left hand rule ?
The current ( positive to negative)
What are the factors affecting the magnitude of the force experienced by the conductor ?
- magnetic field strength ( flux density B )
- current through the conductor
- length of the wire in the field
What happens to the equation F= BIL when the component is not perpendicular to the field ?
BIL sin@ ( component to the perpendicular field )
What is the magnetic flux density ?
Force on one metre of a conductor carrying one amp perpendicular to the field
What is the equation for the force experienced by a moving charge within a magnetic field ?
F= BQV ( sin @ if not perpendicular)
How can the direction of a moving charge be found within the magnetic field ?
Left hands rule
If the particle is negative the direction opposite to what it was initially travelling at
Why does the charged particle have a circular path in a uniform magnetic field ?
Due to the centripetal force experienced as a result of the force and the velocity being perpendicular to each other
Why is work not done when a charged particle is in a uniform magnetic field ?
Force is not acting in the direction of the velocity - no change in the speed and kinetic energy remains constant
How do you derive an equation to find the radius of a charged paricle in a uniform magnetic field ?
As the force BQV provides the centripetal force you can equate it to mv^2 / r
R = mv / Bq
