Electromagnetism Flashcards
all about electrical fields ,magnets ,generators ad power
Number one rule of charges
1.Like chargers repel each other
2.Opposite charges attract each other
what do objects with charge produce ?
an electric field
Electric field lines show what ?
- they show the direction of force(using arrows)
- Strenth of force (using density of lines)
- always draw these lines away from the positive charge as shown in the diagram
- For negative charges the lines points torwads the negative
- if close to the positive charger or denser length of the field lines there will a stronger electrical field
The interaction of Negative and positive charges electric fields
Always away from the positive
torwards the negative
Force on charges in an Electric field
- positive charges feel a force in the direction of the field lines
- Negative charges feel a force opposite the direction of the field lines
The Definition Of ELECTRIC FIELD STRENGTH
the strength of the electric field is a measure of the force the field applies per unit of charge
COLoumb’s Law on how to get the force REquired for Calculation of the gravitational field.
For calculations of elecrtic field for two diffent charges remember
the force remains the same cause newtons third law says there is an equal and opposite reaction for every action
Producing a uniform electric Field
The electric field between two charged parallel plates is found by
Electric Field
1.Created by a charge
2.Pushes positive charges in the direction of the field
3.+ve charges gain electrical potential Energy when moved against the field (work done against the Field)
4.Ep Is converted into Kinetice Energy when +ve charge moves with the field (work done by the field)
Electrical Potential Difference(Voltage) formula
Final Kinetic energy for Particle in electromagnetism
1.Calculate the work first using the formula above
2.FInal Kinetic energy =Initial Kinetic energy -Work done
3.Ignore the numbers
Potential difference in an electrical field
1.V=W/Q
2.W=Vq
In W=Vq what is an eV(electron Volt)?
The energy gained by an electron movin across a 1.00V potential Difference
1.6x10^-19 J=1eV
Commit this to memory
Remember the curves lines on the edge of the plates!
Work in an electric field
If the charged object is moving in the direction it would naturally go in the field, the work is being done by the field.
If it is moving against the natural direction, the work is being done on the field.
If it is moving perpendicular to the field, no work is being done.
the more charge the object has …
The more work we had to do to change its location
Electric work
W=Vq =qEd
q = the amount of substance affected by the field
E = electric field strength
d = the change in location
Earths Magnetic field
LIST three changes that can make an electromagnet More Effective
Explain how an electron could be responsible for the magnetical behavour of a material
a movng charge like a Electron creates a magnetic Field.Certain Magnetic behaviour because of the orbting electrons producing magnetic fields that combine to produce larger Mag fields that extend beyond the structure of the material
ELECTROMAGNETIC FIELDS IN A LONG WIRE,LOOP AND SOLENOID
Important
Parts of A Motor
Important memorise this
why does an electric motor rotate
There is an external magnetic field provides by a permanent magnet or an electromagnet(field coils)
the current is always perpendicular to the magnetic field.
F=NILB were
N=umber of coils where
=force ,
I=current,
L=length of the rotor coil perpendicular to B (m)
B= Magnetic flux density
Calculations
Faraday’s Law
a changing Magnetic flux through a loop will induce an EMF
how to caluculate the Average Flux measured by the voltmeter on a coil’s movement and determine its direction
lenz’s Law
1.A changing magnetic flux induces an EMF(FARADAY’LAW)
2.The Induced EMF drives a current
3.The induced current creates a magnetic field
4.The newly formed magnetic field has a direction that opposes the changing magnetic flux(Lenz’s law)
FARADAY’S LAW CONTINUED
please note
change in flux creates an EMF and an EMF creates A current that CREATES ITS OWN MAGNETIC FIELDS (FARADAY’S) (INDUCED FIELD PUSHES BACK)
GUIDE TO ANSWERING FARADAY’S LAW QUESTIONS
GUIDE TO ANSWERING FARADAY’S LAW QUESTIONS 2
alternitive right hand rule for solenoids
