## IB Physics Glossary

Browse the glossary using this index

Special | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |

**ALL**

## E |
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## Electronvolt is the work done in moving an electron through a potential difference of 1 volt. (d) A charge, q, gains kinetic energy $$q V$$ when it is accelerated through a potential difference $$V$$: $$q V = \frac{1}{2}m v^2$$. | |

## Elevator weight is used to show how the reaction force, between a person standing in an elevator and the floor of the elevator, varies with up/down acceleration of the elevator: Note, the actual weight of the person does not change but an increase or decrease in the reaction force produces a change on the weighing scale in elevator. | |

## Emf or electromotive force, is the total energy supplied by a cell/battery per unit charge as it flows through the cell/battery. (d) | |

## Emissitivity is the ratio of power emitted (per unit area) by a body to the power emitted (per unit area) by a black body of the same dimensions at the same temperature or the ratio of power emitted by a body to the power emitted if it were a black body. (d) | |

## Energy density is the energy liberated per unit mass of fuel consumed. Its unit is Jkg ^{-1}.(d) | |

## Entropyis a system property that expresses the degree of disorder in the system. | |

## Equilibrium position is the position where a particle would remain at rest if not disturbed. (d) | |

## Escape velocity is the velocity that an object needs at the surface of the planet with sufficient kinetic energy to escape the gravitational attraction of the planet. $$v_{esc} = \sqrt{\frac{2GM}{R}} = \sqrt{2Rg}$$ where G is the universal gravitational constant, M is the mass of the planet, R is the radius of the planet and g is the acceleration due to gravity.For a Black Hole, the escape velocity equals c, the velocity of light in empty space. The above equation becomes $$c= \sqrt{\frac{2GM}{R}}$$ and $$R= R_s = \frac{2GM}{c^2}$$ where R_{s} is the Schwarzchild radius. | |

## Explosive collisionsoccur when the total kinetic energy of a system increases. | |

## F |
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## Far point is the most distant point from the eye for which the eye can focus on (assumed to be $$\infty$$). | |