IB physics

what intermolecular forces are present in an ideal gas?

none

what is the relationship between the change in internal energy and the change in temperature?

the change in internal energy is directly proportional to the change in temperature.

What is the equation for the change in internal energy?

∆U = 3/2 NKB∆T

what is the equation for the change in internal energy for ideal gases?

∆U= 3/2 nR∆T

Work done by a Gas

W=PΔV

When a gas expands, work is done by...

the gas on the surroundings. Work in this case is positive

When a gas compresses, work is done by...

the surroundings on the gas. Work done is negative

The area under a P-V curve for a gas gives what?

The work done on or by the gas

First Law of Thermodynamics

Energy can not be created or destroyed. It can only be transformed from one form to another.

What is is the implication of the first law of thermodynamics on gases?

- When energy is put into or removed from a gas, must correspond with an increase or decrease in the internal energy

What is the equation of the first law of themodynamics?

Q = ∆U + W

Describe the graph of an ideal gas at constant pressure

- a horizontal line

- The area under the curve gives the work done

Describe the graph of an ideal gas at constant volume

- a vertical line

- Area under the curve is zero, therefore the work done is zero

Entropy

a measure of the disorder of a system. It measures the number of possible arrangements of particles and their energies

List the states of matter in order of increasing entropy.

solid, liquid, gas

How does entropy change during phase transitions?

- As a substance increases in temperature (melting and boiling) , the particles gain more kinetic energy increases, increasing the particles' vibrations. This increases the entropy. In gases, the particles have the most freedom and distance between particles, which is why they have the most entropy.

- As a substance decreases in temperature, the particles lose kinetic energy and become more ordered. This decreases the entropy and is why solids have the least entropy.

How does entropy change when a solid is dissolved in a solvent?

- the particles become more disorded, therefore the entropy increases.

How does entropy change when a gas diffuses?

- the particles become more disorded as the distance between them increases. The number of ways to arrange the energies increases as well, leading to an increase in entropy.

How does the entropy of a sealed room change when the freezer door is left open?

- A freezer work by removing heat using electrical energy. The heat that is removed is dumped back into the room through coils an the back of the refrigerator. This increases the temperature of the room.

- When the freezer door is open, the warm air flows into the freezer, the freezer tries to remove heat from the the air and releases cool air into the room. While removing heat, heat is released through the coils in the back due to the process above. This results in heat also being released into the room.

- the net change in temperature of the room, is an increase in temperature, increasing the entropy of the room.

Reversible process

A process that can be reversed without leaving any trace on the surroundings. There is no overall change in entropy.

Irreversible process

A process that cannot return to initial state. There is an increase in entropy

Isolated system

A system that neither energy or matter can be transferred in or out.

Non-isolated System

A system in which energy is transferred between the system and its surroundings.

Changes in entropy in a real isolated system

Entropy increases as all processes are irreversible

Changes in entropy in a non-isolated system

The entropy can decrease, as long as there is an equal or greater increase in entropy of the surroundings.

Macroscopic equation for change in entropy

∆S = ∆Q/T

When change in heat is positive, the change in entropy is...

positive

When the change in heat is negaive, the change in entropy is...

negative

The change in entropy for reversible processes is

∆S = 0

∆Q = 0

Microscopic equation for change in entropy

∆S = Kb lnΩ

microstates

a state describes a state or possible of particles in the system.

state

any microscopic or macroscopic property that is known about the system. i.e particle position, particle velocity, energy, volume etc.

what is the number of microstates for the initial volume of an ideal gas?

Ω = 1^N, where N is the number of particles.

what is the number of microstates for the final volume of an ideal gas?

Ω = 2^N, where N is the number of particles.

what is the change in entropy in terms of microstates?

∆S = Kb ln( 2^N)

second law of thermodynamics

total entropy always increases in an isolated system. for a non-isolated system, then entropy of the universe(system + surroundings) must increase.

Clausis second law of thermodynamics

Thermal energy cannont spontaneously transfer from a region of lower temperature to a region of higher temperature.

Kelvin second law of thermodynamics

It is impossible to convert all the energy extracted from a heat reservoir into work. (Some of the energy must be expelled to a colder reservoir, and some is lost to other components.)

Work-energy principle

Work done equals change in kinetic energy.

Fd = ½mv²

Equation for the tension of a mass accelerating upwards

mg - T = ma

Equation for the tension of a mass accelerating downwards

T - mg = ma

What is Coulumb's law?

The force between two point charges is directly proportional to the product of the charges and inversely proportional to the squared distance seperating the two charges.

electric field

Force per unit charge experienced by a small positive charge at that point.

what direction is the force in the electric field

the force is in the direction of the field.

what is the direction of the electric field around a positive charge

the field lines point away from the charge

what is the direction of the electric field around a negative charge

the field lines point towards from the charge

electric potential

The work done per unit charge in bringing a positive test charge from infinity to that point in the field.

electric potential for a positive charge

- has a positive value

- at infinity, V = 0

- as the charge moves closer, V increases

- work is done to bring a small positive test charge closer

electric potential for a negative charge

- has a negative value

- at infinity, V = 0

- as the charge moves aways, V increases

- work is done to pull a small positive test charge away

what is the electric field strength between two parallel plates

E = V/d

what is the electric field around a conducting sphere

the resultant field is the same as though it were a point charge.

electric field in a conducting sphere

the electric field in a conducting sphere is zero.

electric potential in a conducting sphere

it is constant and equal to the potential at the surface.

electric potential energy

The work done moving a charge from infinity to a point in an electric field.

relationship between electric potential energy and electric potential

electric potential is the electric potential energy per unit of charge

electric potential gradient

Rate of change of electric potential with distance. it points in the direction of increasing potential.

equipotential lines

regions of equal potential in an electric field

Equipotential lines are always ___ to electric field lines

perpendicular

electric potential gradient

Rate of change of electric potential with distance. It points in the direction of increasing potential.

what causes a magnetic field?

magnetic flux density

a measure of the strength of the magnetic field defined in terms of the force on a current-carrying conductor at right angles to the field lines

in which direction do magnetic filed lines go

from the north to the south pole

uniform magnetfic field

the strength of the magnetic ffield is the same at all points. The field lines are equally spaced

Describe the magnetic field around a current-carrying wire?

The magnetic field lines are circular rings around the current-carrying wire.

what happens to the magnetic field lines in a current-carrying wire when the current is reversed

the magnetic field lines' directions are reveresed

Right hand grip rule

For a current-carrying wire, the thumb points in the direction of the conventional current, and the direction of the field is given by the direction in which the fingers of the right hand would curl around the wire.

solenoid

A coil of wire that produces a magnetic field when carrying an electric current

How does a solenoid increase the magnetic field strength?

it adds turns in smaller regions of space. this reinforces and increases the magnetic fiel d strength

equation for magnetic force of a current carring wire in a magnetic field

F = BILsinθ

How can you increase the magnetic force?

- increasing the magnetic field strength

- increasing the current in the conductor

- increasing the length of the conductor withing the field

When is the magnetic force the greatest for a current-carrying wire in a magnetic field?

when the wire is perpendicular to the magnetic field.

What is the magnetic force when the current-carrying wire is parallel to the magnetic field?

it is equal to zero

Flemmings Left hand rule

It is used to determine the force on a current-carrying conductor.

Thumb = Force

Second finger = Field

Third Finger = Direction of Current

What direction is a magnetic field when it is denoted by crosses?

The field is going into the page

What direction is a magnetic field when it is denoted by dots?

The field is coming out of the page

When do parallel carrying conductors attract each other?

When the current in the parallel conductors travel in the same direction

When do parallel carrying conductors repel each other?

When the current in the parallel conductors travel in opposite directions

Why do parallel carrying conductors with current in the same direction attract each other?

The outer magnetic fields are reinforced. In the middle, the magnetic fields are partially cancelled out. The magentic field in both wires excert forces on each other, pulling the wires together.

Why do parallel carrying conductors with current in opposite directions repel each other?

The magnetic field reinforces in the middle, but cancel out at outer regions. This results in a strong magnetic field in between the wires.

Force per unit length between two parallel conductors

F/l = μ0 × I2I1/2πr

Magnetic force on a moving charge

F = qvBsinθ

When does a moving charge experience a magnetic force?

When it interacts with an applied magnetic field

When will a moving charge experience a maximum magnetic force?

When the charge travels perpendicular to the magnetic field. sin90 = 0

Does the direction of a particle motion affect the magnitude of its magnetic force?

Yes, it does. Because F, B, and V are perpendicular to each other

How do we determine the direction of the force on a charged particle?

With Flemming's Left Hand Rule

Thumb - direction of the force

Index- direction of magnetic field

Second finger - points in the direction of the current.

What happens when a charged particle moves in a uniform magnetic field?

- the force act perpendicular to the magnetic field and the velocity. This results in a circular path. The magnetic force provides the centripetal force, changing the velocity but not the speed.

What is the motion of charged particles in uniform magnetic fields going into the page?

- positive charges - move in an anticlockwise path

- negative charges - move in a clockwise path

What is the motion of charged particles in uniform magnetic fields coming out of the page?

- positive charges - move in a clockwise path

- negative charges - move in an anticlockwise path

What is the motion of a charged particle in an electric field starting from rest?

It will experience a force causing constant acceleration parallel to the electric field lines.

- positve charges accelerate in the direction of the electric field

- negative charges accelerate in the opposite direction of the electric field.

What is the motion of a charged particle in an electric field with an initial velocity? (Between two charged parallel plates)

The particles will experience a constant electric force and travel in a parabolic trajectory.

- negative charges defelect towards the positive plate.

- positive charges deflect towards the negative plate

- force is the same at all points.

What is the motion of a neutral particle experience in a uniform electric field?

It will expereince no force and move through undeflected

What affects the deflection of a charged particle?

- mass - greater mass equals more defelction and vice versa

- charge - the greater magnitude of charge the greater the deflection and vice versa

- speed - the greater the speed, the smaller the deflection and vice versa.

Motion of a charged particle in an electric and magnetic field

a charged particle moving perpenduiclar to both an electric and magnetic field witl experience a force parrallel to the electric field and perpendicular magnetic field.

Velocity of Charged Particle when the magnetic and electric field are equal

v = E/B

Charge to mass Ratio

Q/m

How to determine the charge to mass ratio

The charge to mass ratio can be determined by investigating its motion in a uniform magnetic field.

Helmsholz coils are used to generate a uniform magnetic field

For a charged particle moving in an electromagnetic field, when is the velocity constant?

when the electric force equals the magnetic force

when is a uniform electric field created

between two oppositely charged parallel plates

oscillation

motion that occurs periodically

frequency

number of oscillations per second