Test 8: Electricity and Magnetism Flashcards
What is electricity?
A phenomena caused by positive and negative charges.
A form of energy most widely used to power machines of all kinds and your brain.
What charges attract and repel?
Opposites attract (+ -) Same charges repel (+ +) (- -)
What is electrostatic electricity?
The study of phenomena related to electrical charges at rest.
What charges can be transferred between two materials?
Negative charges (positive charges remain in place).
What is a conductor?
It is a material or object that allows for the free flow of electrical charges.
What is an insulator?
It is a material or object that impedes the free flow of electrical charges.
What can electrons do?
- Leave or enter an object, creating a net charge on the object
- Move within an object that is a conductor, distributing charges within the object
How does an object gain a charge?
- Friction (rubbing)
- Conduction (contact)
- Induction (approaching)
What happens during friction?
- 2 neutral objects rub together
- Friction pulls the electrons away from one of the objects, transferring them to the other
- Now 2 objects of opposite charges
What is electron affinity?
The direction the negative charges travel is determined by how strong each material is attracting them.
What is an electrostatic series?
It is a list that ranks materials by their electron affinity (ability to gain or lose electrons)
What happens during conduction?
- A charged object touches a neutral one
- The charge of one object will be shared between both objects
- Now 2 objects with the same charge
What happens during induction?
- A charged object gets close to a neutral one
- The charged object will cause movement of charges in the neutral one
- Now one charged object and one dipole (uneven distribution of charges)
- A spark could occur when a charged object is brought really close to a dipole
What is a coulomb?
The unit of measurement for an electrical charge.
What does the force of 2 charged objects at rest depend on?
- The distance between the objects (inversely proportional)
- The amount of charge on each object (proportional)
What is Fe and what is the unit?
- The force between the objects
- Newtons
What is q1 +q2 and what is the unit?
- The amount of charge on the objects
- Coulomb
What is r and what is the unit?
- The distance between the objects
- Metres
What is k and what is the unit?
Constant of proportionality (Coulomb’s Constant)
k = 9 X 10^9 N m2 / C2
How do we calculate the force of energy?
Fe = k q1 q2 / r2
What is a force?
A push or pull that causes a change in motion.
What is a force field?
The pattern in space of how force is felt by other objects.
What is magnetism?
- The phenomena caused by magnets.
- A force like gravity or the and repulsion of electrostatic charges.
What forms a magnetic field?
Electrons flowing in a magnet.
What is a magnet?
An object that can attract other objects containing iron, nickel or cobalt.
What materials are ferromagnetic?
- Iron
- Nickel
- Cobalt
What do all magnets have?
- Two poles: north and south
- A north-seeking pole and a south-seeking pole
Which poles attract and repel each other?
Opposites attract (S N) Same poles repel (S S) (N N)
What is the relationship between the distance and magnetic force of the poles?
They are inversely proportional.
Where are the geographic and magnetic poles on the Earth?
Geographic North and magnetic South are at the top.
Geographic South and magnetic North are at the bottom.
Where does a compass point?
To the geographic North.
What causes most of Earth’s magnetic field?
Moving molten iron in Earth’s outer core.
What are 3 types of substances and describe them?
- Non-magnetic: not attracted or repelled by a magnet
- Magnetic: attracted or repelled by a magnet
- Ferromagnetic: attracted by a magnet, can be temporarily magnetized.
What are magnetic fields?
- The space around a magnet where its field are felt.
What can be used to determine the shape of a magnetic field?
Iron fillings.
What can be used to determine the direction of the lines of force in a magnetic field?
A compass (North of compass points to South of magnet).
What do field lines do of a magnetic field do?
- Converge at the poles
- Point away from North, towards South
- Never cross
What is electromagnetism?
- Magnetization by electrical currents
- The interaction between electricity and magnetism
How do you use the left hand rule?
- Left thumb points in the direction of electron current (points to positive)
- The fingers curl in the direction of the magnetic field lines.
How do you use left hand rule for a solenoid?
- Start at negative
- Wrap your fingers under or over
- Thumb points to North
What are some uses for solenoids?
- Magnetic crane
- Earphones/ speakers/ microphone
- Electric motor
- Electric doorbells
