Magnetism Flashcards
What is the motor effect
When a current-carrying wire is placed at a non-zero angle to the likes of force of an external magnetic field it experiences a force
When is the force due to the motor effect greatest
When the wire is at right angles to the magnetic field
What is magnetic flux density
The strength of the magnetic field
What happens to a rectangular current-carrying coil with n turns in a uniform horizontal magnetic field
Each long side experiences F=BIln
The pair of forces acting on the long sides form a couple with a torque =Fd
What is the d in the torque equation equal to in the field
d=wcos(x)
Where x is the angle the width makes to the field lines
Where w is the width of the coil
What is torque full equation in magnetic field
Torque=BIAncos(x)
What path do charged particles follow in a magnetic field
A circular path as the direction of force is perpendicular to the velocity v
Force on a charged particle in a magnetic field
F=BQv
What is electromagnetic induction
When’s magnet is moved relative to a wire a small current passes through the circuit. This happens because there is an emf induced in the wire
How can induced emf be increased
Moving the wire faster
Using a stronger magnet
Making the wire into a coil
What is the rate of energy Transferred from the induced emf to the components of the circuit equal to
Induced emf x current
Why does electromagnetic induction happen in a wire in terms of electrons in a rod
When the rod is moved across the magnetic field, the magnetic field forces the free electrons in the rod to one end
This makes one end positively charged and the other negatively charged
This is a potential difference across the rod
What is lenzs law
The direction of the induced current is always such as to oppose the change that causes the current
What is the explanation of lenzs law
Energy cannot be created or destroyed
If it went in the direction of the change it would produce potential energy out of no where
What is the induced emf equal to in a conductor when forced through a magnetic field
Emf=BA/dt
What is faradays law
The induced emf in a circuit is equal to the rate of change of flux linkage through the circuit
What is magnetic flux linkage
The number of feild lines cut by a coil with N turns
Why is there a -sign on the induced emf equation
To show that it is opposing the change that causes it as per lenzs law
What is the induced emf when moving a conductor through a field
Emf=Blv
What is the emf equal to when there is a fixed current and a changing magnetic field
NAdB/dt
What is the induced emf in. Rectangular coil moving into a uniform magnetic field
BNlv
What is the graph of induced emf in an alternating current
Emf=(emf0)sin(2pift)
Why is an emf induced in a spinning coil of an electric motor
The flux linkage through the coil changes
