Magnetic Field & Forces Flashcards
Define what is meant by a Magnetic Field.
Is a region where a small, positively charged particle feels a force
How are magnetic fields represented?
With field lines
In which direction do field lines travel?
From NORTH to SOUTH
What does the distance between the field lines represent?
The closer together the lines, the stronger the field.
Draw a diagram of a Bar Magnet.
Draw a Diagram of close together North and South poles.
Draw a Diagram of LIKE poles being pushed towards each other.
The arrow is pouring at a neutral point we’re magnet fields cancel out
What must be true for a Magnetic Field to be around a wire?
Wire must be carrying and electric current, therefore a magnetic field will be created.
What are the field lines like around a Current carrying wire?
What hand do you use to find the Magnetic Field around a Current carrying wire?
Right hand
Show what a Magnetic Field around a Solenoid.
What will a wire carrying a Current in a magnetic field experience?
A force
Show a diagram of a Current carrying wire within a Magnetic Field.
Which rule to you use to find the Resultant Force of a Current carrying wire within a Magnetic Field?
Flemings Left Hand Rule
In which direction does the force act on a wire carrying a Current within a Magnetic Field?
Perpendicular to the Magnetic Field
What happens to the Force if the Current carrying wire is parallel to the Magnetic Field?
There is no force
State the components of Flemings Left-Hand Rule.
THUMB - Force (Motion)
First Finger - Magnetic Field
SeCond Finger - Conventional Current (positive to negative)
Remember - FBI
Which way does Conventional Current go?
Positive to Negative
The force on a wire is proportional to…
The Flux Density
Define Magnetic Flux Density.
The force on one metre of wire carrying a Current of one amp at right angles to the Magnetic Field
What is the Equation symbol for Magnetic Flux Density?
B
What is Force Proportional to when a Current is at 90 degrees to the Magnetic Field?
Force is proportional to the…
- Current, I
- Length of wire in the field, l
- Flux Density, B
What is the equation for the force of a Current carrying wire when it is 90 degrees to the magnetic field?
F = BIL
F - Force (N)
B - Flux Density (T, Tesla’s)
L - Length of wire in the field (m)
Is Flux Density a Scalar or a Vector?
Vector
What is Flux Density measured in?
Teslas, T
When is the Force of a Current carrying wire within a Magnetic Field at its greatest?
When it is perpendicular to the field
What is the equation for the Force of a wire acting an angle to the magnetic field?
F = BIL sin θ
Forces act on (……………..) in Magnetic Fields
Charged Particles
Define Electric Current.
Flow of charge, Q per unit time.
What is the equation for the velocity of a charged particle?
V = L / t
V - Velocity
L - Distance travelled
t - Time
Derive the equation F = Bqv.
Use F = BIL
And I = Q / t
And L = vt
Substitute into F = BIL
F = B q/t vt - the t’s cancel out.
F = Bqv or F = Bqv sin θ
What is the equation for the Force acting on a charged particle in a magnetic field?
F = Bqv sin θ
F - Force (N)
B - Magnetic Flux Density (T)
q - charge on the particle (C)
v - Velocity of the particle (ms*-1)
θ - angle between the current and field lines
