Topic 3B - Magnetic Fields Flashcards
Define the term Magnetic Field
A region in space where a particle experience a force due to it’s magnetic condition
Explains what forms magnetic field and compare this to the formation of electric fields
Magnetic field are formed by moving electric charges and hence by electric currents.
In comparison, electric fields are formed by static charged particles.
What is conventional current?
The flow of positive particles. Opposite to the flow of the negative particles.
Conventional current is the standard units.
State the direct of a magnetic field
The direction that the north pole of a small compass would point if placed in the field.
i.e. north to south
Describe the field inside a solenoid
The field inside a solenoid is uniform. If the flow of the current around the solenoid is given, the location of the north pole of a solenoid can be found using the right-hand grip rule or vice versa
State the equation that can be used to find the magnitude of a magnetic field around a straight current carrying wire.
Do one question
B = u/2pi I/r
Units = Tesla (T) u/2pi = 2 x 10^-7
Define the magnitude of magnetic field
The force per unit current element
Write equation for force on current carrying wire when place in an external magnetic field.
Do one question
F = I (delta)L B sin0
where 0 is the angle of the wire to the external field
What rule can be used find the direction of force on a current carrying wire in a field
Right-hand slap rule
Fingers - direction of external B
Thumb - direction of conventional current in the wire
Palm - direction of force on the wire
Describe the equation that gives the force on a charged particle in the B field.
F = q v B sin0
where 0 is the angle between the particle’s direction of motion and the external magnetic field
Describe and explain what occurs when a particle enters a B field at 90 degrees to the field.
When a particle enters a magnetic field at 90 degrees to the field it experiences a force perpendicular to its velocity. When a particle experience a constant force perpendicular to its motion it undergoes uniform circular motion. Therefore, the particle will move in a circle.
Derive the equation for the radius of the uniform circle motion of a particle in a B field.
F(B) = F(c)
q v B sin0 = m v^2 / r
sin90 = 1
q v B = m v^2 / r
q B = mv/r
r = mv/ qB
Describe the force on partciel travelling parallel or antiparallel to the B field.
The magnetic field will have no impact on this particle as sin0 = 0.
What are cyclotrons?
They are particle accelerators and are used for scientific research, industrial and medicinal purposes.
Derive the period of a particles revolution in a cyclotron.
What does this equation tells us about the period?
Explain this.
Sub V = 2pi x r / T
into the radius equation r = mv / qB
