Electromagnetism Flashcards
What is magnetic field?
It is the region of space where a magnetic pole, moving charged particle or current-carrying conductor will experience a magnetic force
How to find direction of magnetic field at a point?
Tangent to a field line or curve at a point
What is the strength of magnetic field indicated by?
Density of magnetic field lines
- magnetic field lines close together –> stronger
- magnetic field lines further apart –> weaker
What direction do magnetic field lines point in?
Away from North towards South pole
How to tell if magnetic field is uniform?
Lines of force are parallel
Why do magnetic field lines not intersect?
There can only be one direction for field at any point
How do magnetic field differ from electric field?
Magnetic field only acts on moving charges while electric field is produced by static charges
What does a dot represent?
Coming out of the page
What does a cross represent?
Going in the page
What is magnetic flux pattern of current carrying conductor?
Concentric circles, radiating outwards with increasing radius
How to determine direction of magnetic field lines for current carrying conductor?
Right Hand grip rule
- If thumb is current, fingers is direction of magnetic field
- if fingers is current, thumb is direction of magnetic field
What is the equation for magnetic flux density around straight conductor?
B = μI/2πd
μ = permittivity of free space
d = perpendicular distance from point to straight conductor (basically shortest distance)
What direction does a compass needle point in?
Direction of net magnetic field
What is the earth’s magnetic field caused by?
Electric currents circulating within the core of the earth
Where is magnetic south pole of the earth?
At geographical north
Where is the magnetic north pole of the earth?
At geographical south
How does magnetic field lines travel for earth?
From magnetic north to magnetic south, from geographical south to geographical north
What is the magnitude of the magnetic flux density at the centre of circular coil?
B =μNI / 2r
N = number of turns of the coil
What does a solenoid consist of?
Many flat circular coils stacked together side by side
What is the magnitude of the magnetic flux density inside a solenoid?
B = μnI
n = N / L (number of turns per unit length)
What does the insertion of ferromagnetic material change?
It changes the permeability of free space μ0 to permeability of the material μ (where μ > μ0)
What is the effect on the magnetic flux density of a current carrying solenoid when a ferrous core is inserted into it?
The magnetic field generated by the current in the solenoid aligns the domains of magnetic dipoles in the ferrous core. The magnetic dipole produce their own magnetic field lines, thus strengthening the existing magnetic flux density by a few thousand times and a much larger magnetic flux density will be created
What is magnetic flux density?
Magnetic flux density is the force per unit current per unit length acting on an infinitely long current-carrying conductor placed perpendicular to the magnetic field
What is one tesla?
One tesla is the force per unit length of one newton per metre acting on a straight conductor carrying one ampre of current placed normal to the magnetic field
What does a mass spectrometer consist of?
Both velocity selector and deflection chamber
Is magnetic flux density scalar or vector?
Vector
What is the work done of an electron passing through a magnetic field?
There is no work done because W=Fd, where force is in the direction of distance. Since magnetic force is always perpendicular to direction of velocity (direction of electron), therefore work done = 0. Change in kinetic energy is also 0.
