Module 6 Part 1 Flashcards
What is an electric field
An electric field is an area where anything with charge will experience an attractive or repulsive force
What is electric field strength
Electric field strength is the force experienced per unit charge and therefore can be written as E=F/Q
Where do electric field lines point from and to
From positive to negative
What is the electric field pattern for a point charge and how does it compare to that of two plates
A point charge will have a radial pattern for its field whereas two plates will create a uniform electric field between them where all the field lines will be equally spaced
What is a coulomb
A coulomb is the SI unit for charge and it is given the letter Q
What is Coulomb’s law
Coulomb’s law is an inverse square law which can be used to find the magnitude of force between two charges: F=k(q1q2)/r^2. This means that as distance increases force decreases
What is the equation for electric field strength in a uniform electric field
Electric field strength-E=potential difference-v/distance-d
What was Milikans oil drop experiment and what did he discover
Milikans oil drop experiment was when R. A Milikan fired droplets of oil into a chamber of ionized air to give the oil a positive charge, then used a negative plate at the bottom to counteract gravity and suspend the droplets in the air. The magnitude of the charge on the negative plate could be changed and then after observation of the effects that different voltages had he deduced the charge on the droplets was a multiple of 1.6x10^-19 C or e
What is electrical potential
Electrical potential is defined as the work done per unit charge to move that object in a direction opposing the electrostatic force
Rule for electricity and magnets: like charges/poles ______ opposites _________
repel, attract
Magnetic fields go from _____ to _____
North, south
What is a magnetic field
An area where an object that can be magnetized experiences a force
What is magnetic flux density
Magnetic flux density is essentially the magnetic field strength, however unlike electric and gravitational field strength it is not the force per unit x, it is the force per unit amp meter multiplied by sin of the angle between the magnetic field and direction of current
What is the equation for magnetic flux density
B=F/ILsinθ (sinθ disappears if current is perpendicular to magnetic field)
What happens to a charged particle entering a uniform magnetic field
It changes direction and moves in circular motion due to the magnetic force acting as a centripetal force and the velocity moving it round in a circle
What is the equation for the radius of a charged particles circular motion and how do you arrive there
r=(mv)/BQ
You set the circular motion equation for force equal to the magnetic field equation for force:
(mv^2)/r=BQv and then the v’s cancel and you can re arrange for r
What is a velocity selector
A system with two charged plates with a vacuum in between therefore creating a electric field, with a magnetic field perpendicular to this. A particle then travels through a slit into this area and if they are too fast or too slow they will be deflected by the fields and not travel through to the other side.
What is faradays law
The magnitude of the induced emf is directly proportional to the rate of change of magnetic flux linkage
What is lenz law
The induced emf is always opposite to the change that is making it (conservation of energy)
What equation do you arrive at by combining faradays law and lenz law and state each letters meaning
E=-(NΦ)/t
E=emf
N=number of turns
Φ=magnetic flux
t=time
What is a capacitor
A capacitor is an electrical component which stores charge
What is capacitance and state the equation
Capacitance is defined as the charge stored per unit of potential difference
C=Q/V
What is a capacitor made of and how does it work
A capacitor is two plates with an insulating dielectric between them
How it works is:
The electrons flow onto one side and then repel the electrons on the other plate but don’t actually pass over as the insulating layer stops that
How do you add capacitors in series
1/C T= 1/C1 + 1/C2 + 1/C3
How do you add capacitors in parallel
C T= C1 + C2 + C3
What is electrical potential
The energy needed to move a point charge to a place from a point of infinity
What is a transformer
A transformer is a device which increases or decreases the potential difference
What is a transformer made up of and how does it work
A transformer is made up of two coils with AC current running through them both wrapped around an iron core
The primary coil magnetizes and demagnetizes the iron core which in turn induces current one way and then the other way in the secondary coil
What is the transformer equation
P number of turns/ S number of turns = P voltage/ S voltage
What are three ways you can make a transformer more efficient and briefly explain
Laminated iron core- reduces eddy current (current in iron core)
Soft iron core-allows easier magnetization
Low resistance wires-less energy lost to heating
