magnetism day 2 charged particles moving through magnetic fields
TRANSCRIPT
When a charged particle travels through a magnetic field, it “might” experience a force.
When will it?
When won’t it?
When a component of the magnetic field is perpendicular to the particle’s velocity.
When the velocity of the particle and the velocity are either PARALLEL or ANTI-PARALLEL.
Right Hand Rule #1 (or RHR-1):
Finding the direction of the force exerted on a positive charge moving through a magnetic field
Charged particle’s sign: +
Motion direction: East
Dir. of Magnetic Field: North
Dir. of Magnetic Force
Charged particle’s sign: -
Motion direction: East
Dir. of Magnetic Field:
Dir. of Magnetic Force South
Charged particle’s sign: -
Motion direction: North
Dir. of Magnetic Field: Downward
Dir. of Magnetic Force
Charged particle’s sign:
Motion direction: South
Dir. of Magnetic Field: West
Dir. of Magnetic Force Upward
Some Examples
More ExamplesCharged particle’s sign: -
Motion direction: West
Dir. of Magnetic Field: East
Dir. of Magnetic Force
Charged particle’s sign: +
Motion direction: Upward
Dir. of Magnetic Field: West
Dir. of Magnetic Force
Charged particle’s sign:
Motion direction: South
Dir. of Magnetic Field: Upward
Dir. of Magnetic Force West
Charged particle’s sign: +
Motion direction:
Dir. of Magnetic Field: South
Dir. of Magnetic Force East
OK, so RHR-1 gives us the direction of the force. But since force is a
vector, can we find the MAGNITUDE of the force?
qvBFmagnetic
Magnetic Field Strength (measured in Teslas, T)
Velocity of the particle (m/s)
Charge of the particle (C)
NOTE: This equation is only valid if B and v are perpendicular to each other!!!
What exactly is a Tesla?
• 1 T = _____________
• 1T is REALLY big. So we often us prefixes like mT, T, or nT.
• The earth’s magnetic field is soooooo small that we often use a term called a GAUSS (G) to measure it.
• 1 G = 0.1mT (and the earth’s magnetic field is ~ .1-.3 G)
€
1N /(C⋅ ms )
But what if v and B are NOT perpendicular?
sinqvBFmagnetic
Magnetic Field Strength (measured in Teslas, T)
Velocity of the particle (m/s)
Charge of the particle (C)
The angle between v
and B
What would happen if ……
What would you have to do to make the path helical?
+ -
qB
mvr
r
mvqvBFF
r
mvFqvBF
cmag
cmagnetic
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