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# P - 4/5 Definitions

### OCR Physics A2 - Unit 4 & 5 Definitions

Question | Answer |
---|---|

Capacitance | The charge stored per unit potential difference. (Farads) |

Farad | One coulomb per unit volt. |

Time Constant | The time constant of a circuit containing capacitance C and a resistor of resistance R is given by t = CR. |

Intensity | The power per unit cross-sectional area. |

Nucleon | A nuclear particle, either a proton or a neutron. |

Activity | The rate of decay of nuclei. |

Decay Constant | The probability per unit time that a nucleus will decay. |

Random | Decay of a nucleus cannot be predicted. |

Spontaneous | Radioactive decay cannot be induced. |

Half-Life | The time taken for the activity of the source to decrease by half. |

Binding Energy | The minimum energy required to split a nucleus up into all of it's protons and neutrons. |

Electric Field Strength | Force per unit positive charge. |

1 Tesla | The magnetic flux density in a 1m wire carrying 1A experiences a force of 1N. |

Faraday's Law | The magnitude of the induced e.m.f. is equal to the rate of change of magnetic flux. |

Lenz's Law | The direction of the induced e.m.f. opposes the change that caused it. |

Newton's First Law | An object will remain at rest or continue to move with a constant velocity unless acted upon by an external force. |

Newton's Second Law | The rate of change of momentum of an object is directly proportional to the resultant force action on it and in the same direction. |

Newton | One newton is the force that gives a mass of 1kg an acceleration of 1ms⁻². |

Newton's Third Law | If body A exerts a force on body B, body B will exert an equal and opposite force on body A. |

Principle of Conservation of Momentum | In any direction, in the absence of external forces, the total momentum of a system remains constant. |

Impulse | Force x time for which the force acts. |

Elastic Collision | Momentum and Kinetic Energy are conserved. |

Inelastic Collision | Momentum is conserved, but Kinetic Energy is not. |

Radian | The angle subtended at the centre of a circle by an arc of length equal to the circle's radius. |

Field | The region in which a force operates. |

Gravitational Field Strength | Force per unit mass. |

Newton's Law of Gravitation | The gravitational force of attraction between two bodies is directly proportional to the product of their masses, and inversely proportional to the square of the distance between them. |

Kepler's Third Law | The period of a planet squared equals the mean radius of its orbit cubed. |

Geostationary Satellite | Travels over the equator with a period of 24 hours. |

Displacement | The distance an object has moved from it's equilibrium position. |

Amplitude | The maximum displacement. |

Frequency | The number of oscillations per unit time at any point. |

Period | The time for one complete patter of oscillation to take place at any point. |

Simple Harmonic Motion | An object that has an acceleration proportional to it's displacement, and is always accelerating towards the equilibrium position. |

Damping | Deliberately reducing the amplitude of an oscillation. |

Light Damping | The period of oscillation is almost unchanged, but the amplitude gradually decreases. |

Resonance | A large amplitude oscillation caused when an object is being driven at it's natural frequency. |

Internal Energy | The sum of the random microscopic kinetic and potential energies of a body. |

Ideal Gas | Only has internally energy in the form of random kinetic energy. |

Specific Heat Capacity | The energy required to raise the temperature of 1kg of mass by 1K. |

Specific Latent Heat of Fusion | The energy required per unit mass to change it from a solid to a liquid at constant temperature. |

Specific Latent Heat of Vaporisation | The energy required per unit mass to change it from a liquid to a gas at constant temperature. |

Boyle's Law | For a fixed mass of gas at a constant temperature, the pressure is inversely proportional to the volume. |

Created by:
Sparksy