Module 6 Part 1

Question 1

What is an electric field

Answer 1

An electric field is an area where anything with charge will experience an attractive or repulsive force

Question 2

What is electric field strength

Answer 2

Electric field strength is the force experienced per unit charge and therefore can be written as E=F/Q

Question 3

Where do electric field lines point from and to

Answer 3

From positive to negative

Question 4

What is the electric field pattern for a point charge and how does it compare to that of two plates

Answer 4

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

Question 5

What is a coulomb

Answer 5

A coulomb is the SI unit for charge and it is given the letter Q

Question 6

What is Coulomb’s law

Answer 6

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

Question 7

What is the equation for electric field strength in a uniform electric field

Answer 7

Electric field strength-E=potential difference-v/distance-d

Question 8

What was Milikans oil drop experiment and what did he discover

Answer 8

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

Question 9

What is electrical potential

Answer 9

Electrical potential is defined as the work done per unit charge to move that object in a direction opposing the electrostatic force

Question 10

Rule for electricity and magnets: like charges/poles ______ opposites _________

Answer 10

repel, attract

Question 11

Magnetic fields go from _____ to _____

Answer 11

North, south

Question 12

What is a magnetic field

Answer 12

An area where an object that can be magnetized experiences a force

Question 13

What is magnetic flux density

Answer 13

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

Question 14

What is the equation for magnetic flux density

Answer 14

B=F/ILsinθ (sinθ disappears if current is perpendicular to magnetic field)

Question 15

What happens to a charged particle entering a uniform magnetic field

Answer 15

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

Question 16

What is the equation for the radius of a charged particles circular motion and how do you arrive there

Answer 16

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

Question 17

What is a velocity selector

Answer 17

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.

Question 18

What is faradays law

Answer 18

The magnitude of the induced emf is directly proportional to the rate of change of magnetic flux linkage

Question 19

What is lenz law

Answer 19

The induced emf is always opposite to the change that is making it (conservation of energy)

Question 20

What equation do you arrive at by combining faradays law and lenz law and state each letters meaning

Answer 20

E=-(NΦ)/t
E=emf
N=number of turns
Φ=magnetic flux
t=time

Question 21

What is a capacitor

Answer 21

A capacitor is an electrical component which stores charge

Question 22

What is capacitance and state the equation

Answer 22

Capacitance is defined as the charge stored per unit of potential difference
C=Q/V

Question 23

What is a capacitor made of and how does it work

Answer 23

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

Question 24

How do you add capacitors in series

Answer 24

1/C T= 1/C1 + 1/C2 + 1/C3

Question 25

How do you add capacitors in parallel

Answer 25

C T= C1 + C2 + C3

Question 26

What is electrical potential

Answer 26

The energy needed to move a point charge to a place from a point of infinity

Question 27

What is a transformer

Answer 27

A transformer is a device which increases or decreases the potential difference

Question 28

What is a transformer made up of and how does it work

Answer 28

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

Question 29

What is the transformer equation

Answer 29

P number of turns/ S number of turns = P voltage/ S voltage

Question 30

What are three ways you can make a transformer more efficient and briefly explain

Answer 30

Laminated iron core- reduces eddy current (current in iron core)
Soft iron core-allows easier magnetization
Low resistance wires-less energy lost to heating