Magnetic fields Flashcards
What does a current-carrying conductor produce?
Its own magnetic field.
When does a current-carrying conductor experience a force in a magnetic field?
When the current is perpendicular to the magnetic field lines.
What happens to a copper rod in a magnetic field when current passes through it?
It experiences a force and moves.
What is magnetic flux density also known as?
Magnetic field strength.
What is the unit of magnetic flux density?
Tesla (T).
State the equation for force on a current-carrying conductor in a magnetic field.
F = BIL
What does F = BIL stand for?
F = Force (N), B = Magnetic flux density (T), I = Current (A), L = Length of conductor in the field (m).
What is the relationship between current, magnetic field strength and force?
Greater current or magnetic field strength results in greater force.
What part of the conductor should be considered in F = BIL?
Only the length within the magnetic field.
What is the direction of the force relative to current and field?
Perpendicular to both current and magnetic field.
When is there no force on a current-carrying conductor?
When the current is parallel to the magnetic field.
Explain what each finger represents in Fleming’s Left Hand Rule.
Thumb = Force (F), First finger = Magnetic field (B), Second finger = Current (I).
What does a dot symbol represent in magnetic field diagrams?
Field coming out of the page.
What does a cross symbol represent in magnetic field diagrams?
Field going into the page.
Using Fleming’s left-hand rule: If B = into the page and F = down, what is the direction of I?
Right to left.
How is the magnetic force on a negative particle different from a positive one?
Direction is opposite due to opposite current flow.
Draw and explain the direction of magnetic force on positive and negative particles in a B field.
It is provided in the document.
What is the definition of magnetic flux density?
Force per unit current per unit length on a conductor perpendicular to the magnetic field.
What is the equation for magnetic flux density?
B = F / (IL)
What is the definition of 1 Tesla?
Force per unit length of 1 N/m on a wire carrying 1 A perpendicular to a 1 T field.
What is the equation for the force on a moving charge?
F = BQv
In F = BQv, what does each variable represent?
F = Force (N), B = Magnetic flux density (T), Q = Charge (C), v = Speed (m/s).
When will a moving charged particle not experience magnetic force?
When it moves parallel to the magnetic field.
What direction is the magnetic force on an electron moving into a page with B into the page?
Upward.
State the equation for centripetal force.
F = mv² / r
How is the magnetic force related to centripetal force for a charged particle in circular motion?
They are equal.
State the equation for the radius of a circular path in a magnetic field.
r = mv / BQ
How does particle speed affect the radius of the circular path?
Higher speed means larger radius.
How does particle mass affect the radius of the circular path?
Greater mass means larger radius.
How does particle charge affect the radius of the circular path?
Greater charge means smaller radius.
How does magnetic field strength affect the radius of the circular path?
Stronger field means smaller radius.
What is a cyclotron?
A particle accelerator using circular paths and magnetic fields.
Name two uses of cyclotrons.
Producing medical isotopes and high-energy beams for radiotherapy.
What components does a cyclotron have?
Two ‘dees’, magnetic field, alternating potential difference.
Describe how a cyclotron accelerates particles.
Particles spiral outward, accelerated each time they cross the gap.
Why is an alternating potential difference used in a cyclotron?
To continuously accelerate particles across the gap.
