IB Physics Topic 2 Definitions

This page contains our IB Physics definitions for topic 2. By learning each one of these definitions, you will fully cover the content for IB Physics 'The Particulate Nature of Matter'.
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Adiabatic Process

A process with no heat transfer, where the system's temperature changes due to compression or expansion

Albedo

It is the the ratio of reflected power to total incident power

Ammeter

This device measures the current of the circuit over the portion it is in series with

Avogadro's number

It is the number of particles (6.022 x 1023) in one mole of a substance

Battery

It is one or more connected cells converting chemical energy into electrical energy

Black body

It is a perfect emitter, absorber, and radiator

Black body radiation

It is the radiation emitted from a black body

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Carnot Engine

A theoretical engine with maximum possible efficiency, operating through adiabatic and isothermal processes

Charge capacity

It is the amount of electrical energy it can produce in its lifetime

Circuit

It is the path a current follows

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Cold Reservoir

A constant source of low temperature that absorbs thermal energy from the heat engine

Conduction

It is the transfer of thermal energy via direct collisions between molecules, thus passing kinetic energy from one molecule to another

Convection

It is the movement of thermal energy in a fluid

Convection current

The cyclical movement of expanding and rising hot and less dense fluid and the condensation and sinking of cold and denser fluid

Electric cell

It is a device that houses an internal chemical reaction that converts chemical energy into electrical energy

Electromotive force

It is the total potential difference per unit charge, including the voltage to power the cell and external components

Emissivity

It is the ratio of emission intensity of the object to the emission intensity of a black body

Enhanced greenhouse effect

It is the increase in greenhouse effect as a result of human activity

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entropy

The measure of distribution of available energy among particles, measured in JK-1mol-1

Global warming

It is the increase in Earth's mean temperature

Greenhouse effect

It is the process by which atmospheric gases absorb infrared radiation emitted from Earth and re-emit them back down to warm the atmosphere and Earth's surface

Greenhouse gases

They are the atmospheric gases that contribute to the greenhouse effect

heat

It is the total kinetic energy of all particles in an object

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Heat Engine

A device that converts thermal energy into work through cyclical processes involving a hot and a cold reservoir

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Hot Reservoir

A constant source of high temperature that releases thermal energy to the heat engine

Ideal ammeter

It is an ammeter with zero resistance

ideal gas

It is a gas that follows the gas laws

Ideal voltmeter

It is a voltmeter with infinite resistance

internal energy

It is the total energy of all particles in an object

Internal resistance

It is the resistance inside the cell

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Isobaric Process

A process occurring at constant pressure, with changes in volume

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Isochoric Process

A process occurring at constant volume, with changes in pressure

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Isothermal Process

A process occurring at constant temperature, involving heat transfer to maintain the temperature

Light-dependent resistor

This device's resistance is dependent on the amount of light shining on it; when light shines on it, its resistance decreases

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Microstate

A specific configuration of particles in a system, with entropy related to the number of possible microstates

molar mass

The mass of one mole of atoms, expressed as M and measured in g/mol

mole

It is the amount of a substance in terms of the number of particles

Non-ideal ammeter

It is an ammeter with a constant but non-zero resistance

Non-ideal voltmeter

It is a voltmeter with a constant but finite resistance

Non-ohmic device

It is a device that does not remain at a constant temperature, does not have a current proportaiontl to voltage, and thus a changing resistance

Ohmic device

It is a device that remains at a constant temperature, has a current proportional to voltage, and thus a constant resistance

Parallel circuit

It is a circuit with devices aligned in a branched loop

Perfect cell

It is a cell with 100% efficiency in the conversion of chemical to electrical energy

Potential divider

This is a device used in circuits to measure the voltage across a resistor

Potentiometer

This device is used as a potential divider, but its resistance must be significantly smaller than any resistor's

Power

It is the energy difference per unit time or energy difference per charge flow

pressure

It is the force per unit area of container wall

Primary cell

It is a cell with a non-reversible internal reaction, meaning it is not rechargeable

Radiation

It is the emission of electromagnetic waves from an object

Resistance

It is the ratio of potential difference to current

Resistivity

It is the amount of resistance a material has based on its length and cross-sectional area

Resistor

It is a device with a constant resistance

Secondary cell

It is a cell with an internal reaction reversible with electricity, meaning it is rechargeable

Series circuit

It is a circuit with devices aligned in one continuous loop

Solar constant

It is the incident solar intensity above the Earth's surface at a right angle to the rays

specific heat capacity

The measure of how much energy a unit mass of a substance takes to be raised by 1K/1°C

specific latent heat

It is the energy absorbed or released by a kg of a substance during a phase change

specific latent heat of fusion

It is the energy absorbed by a kg of substance when it changes from solid to liquid

specific latent heat of vaporization

It is the energy absorbed by a kg of substance when it changes from liquid to gas

Switch

This device breaks the circuit when it is open, and thus no current runs. When it is closed, it completes the circuit and allows current to run

temperature

It is the average kinetic energy of an object's particles

Terminal voltage

It is the maximum voltage a cell can produce

thermal capacity

It is the energy required to raise an object's temperature by 1 K

Thermal conductor

It is a material that is able to conduct thermal energy well

Thermal energy transfer

It is the movement of thermal energy from a hot object to a cold object

thermal equilibrium

It is the state at which two objects are at the same temperature

Thermal equilibrium

It is the state of absorbing power at the rate of emission to maintain a constant temperature

Thermal insulator

It is a material that is not able to conduct thermal energy well

Thermal radiation

It is the emission of infrared waves from an object

Thermistor

This device’s resistance is dependent on its temperature. Most types decrease in resistance when their temperature increases

Variable resistor

This device’s resistance can be manually changed

Voltmeter

This device measures the voltage over the portion of a circuit it is parallel with

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