Magnetic Fields
Thumb = force exerted by current in a mag field
First Finger = Field
Second Finger = Convential Current
What is Fleming's Left Hand Rule?
The right hand grip rule can be used to show...
The direction of a magnetic field around a current carrying wire.
The direction of the magnetic field through a coil.
Force on a current carrying wire = ...
Magetic Flux density x Length of conductor within magnetic field x Current through conductor
Lenz's Law states....
The direction of the induced current is always such as to oppose the change that causes it.
Which of the following will experience a force?
A neutron moving through a magnetic field
An electron moving through an electric field
A proton moving through a magnetic field
A qui-gon moving through a midichlorian field
The electron and the proton
As a car acclerates, what happens to the back EMF in the electric motor?
How does this affect the current in the motor?
How does this affect the torque of the motor?
Back EMF increases as the car speeds up, as more flux is being cut per second by the coil in the motor.
The current is therefore reduced.
There is less magnetic force exerted on the coil and so reduced torque.
An electron has momentum of 1.822 x 10-23 Kgm/s and passes through a magnetic field. What would the field strength need to be to cause it to move in a circle with a diameter of 100 micro meters?
2.28T
A 12V, 48W lamp lights at its normal brightness when connected to a source of alternating pd.
What is:
The RMS current through it.
The peak current through it.
The peak pd across it.
Irms = 4A
I0 = 5.66A
V0 = 17V
How does a velocity selector work in a mass spectrometer, and what variables govern the speed of particles which are allowed through?
Electric force and magnetic force are balanced for a charge moving at the correct velocity.
v=E/B
A transformer has 2500 turns of wire in the primary coil and 500 turns in the secondary.
The transformer is only 80% efficient.
The primary coil is connected to the mains (230V), if the current output required is 4A, what would the input current need to be?
The input current would need to be 1A