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# MCAT Physics Ch 5

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

Coulomb | SI unit of charge |

Charge of Protons and Electrons | e = 1.60 x 10^-19 C |

Note About Protons And Electrons | They have different masses |

Attractive Forces | Forces that opposite charges exert |

Repulsive Forces | Forces that like charges exert |

Conducts | Allow the free and uniform passage of electrons when charged |

Insulators | Resist the movement of charge and will have localized areas of charge that do not distribute over the surface of the material. |

Coulomb's Law | Gives the mag. of the electrostatic force between two charges. The force vector ALWAYS points along the line connecting the centers of the two charges. |

Electric Field | Generated by every stationary charge, which can exert forces on other charges |

Electric Field (in depth) | Ratio of the force exerted on a test charge to the mag. of the charge. |

Field Lines | Representation of electric field vectors which radiate outward from positive source charges and radiate inward to negative source charges |

Note About Positive and Negative Test Charges And Field Lines | Positive test charges will move in the direction of the field lines, while negative test charges will move in the direction opp. of the field lines. |

Electrical Potential Energy | Amount of work required to bring the test charge from indef. far away to a given position in the vicinity of a source charge. |

Note about two like charges in an system | The electrical potential energy will increase when these two like charges move towards each other, or when two opposite charges move further apart. |

Note about two opp. charges in a system | The electrical potential energy will decrease when two opp. charges move toward each other or when two like charges move further apart. |

Electrical Potential | Electrical potential energy per unit charge |

Note about different points in the space of an electric field surrounding a source charge | They will have different electrical potential values. |

Voltage (potential difference) | Change in electrical potential that accompanies the movement of a test charge from one position to another. This is path independent, and only depends on initial and final positions of the test charge. |

Unit for Electrical Potential and Voltage | Volts |

Note About Test Charges | They will move spontaneously in whatever direction results in a decrease in their electrical potential energy. ex: Pos. test charges move spon. from high potent. to low potent. ex: Neg. test charges from spon. from low potent. to high potent. |

Equipotential Lines | Designate the set of points around a source charge or multiple source charges that have the same electrical potential. |

Note About Equipotential Lines and Electric Field Lines | Equipotential lines are ALWAYS perpendicular to electric field lines. |

Note About Work On DIFFERENT Equipotential Lines | Work will be done when a charge is moved from one equipotential line to another. The work is independent of the pathway taken between the lines. |

Second Note About Work The SAME Equipotential Lines | Work will be done when a charge is moved from one point on an equipotential line to another point on the same equipotential line. |

Electric Dipole | Generated by two charges of opposite sign that is separated by a distance, d |

Note About A Dipole In An External Electric Field | An electric dipole experiences a net torque until it is aligned with the electric field vector. |

Note About Electric Field And Translational Motion | An electric field will not induce translational motion in the dipole regardless of its orientation with respect to the electric field vector. |

Magnetic Fields | Fields created by magnets and moving charges. |

SI Unit For Magnetic Field | Tesla (T: 1 T = 1000 gauss) |

Diagmagnetic Materials | Possess no unpaired electrons and are slightly repelled by a magnet. |

Paramagnetic Materials | Possess some unpaired electrons and become weakly magnetic in an external magnetic field. |

Ferromagnetic Materials | Possess some unpaired electrons and become strongly magnetic in an external magnetic field. |

Notes About Poles For Magnets And Field Lines | Magnetics have a north and south pole. Field lines point from the north to the south pole. |

Note About Current-carrying Wires | They create magnetic fields that are concentric circles that surround the wire. |

Note About External Magnetic Fields | They exert forces on charges moving in any direction except parallel or antiparallel to the field. |

Note About Point Charges And A Uniform Magnetic Field | Point charges can undergo circular motion in a uniform magnetic field. |

Centripetal Force | Magnetic force acting on a point charge. |

Direction of Magnetic Force | Determined using right-hand rule. |

Lorentz Force | Sum of the electrostatic and magnetic forces acting on a body. |

Eq. 5.1: Coulomb's Law | Fe = kq1*q2 / r^2. |

Eq. 5.2: Electric Field | E = Fe / q = kQ / r^2 |

Eq. 5.3: Electrical Potential Energy | U = kQq / r |

Eq. 5.4: Electrical Potential (From Electrical Potential Energy) | V = U / q |

Eq. 5.5: Electrical Potential (From Source Charge) | V = kQ / r. For a positive source charge, V is positive. For a negative source charge, V is negative. |

Eq. 5.6: Voltage | Del. V = Vb - Va = Wab / q |

Eq. 5.7: Electrical Potential Near A Dipole | V = (kqd / r^2) * cos(angle) |

Eq. 5.8: Dipole Movement | p = qd. p is the point from the positive charge toward the negative charge. |

Eq. 5.9: Electric Field On The Perpendicular Bisector Of A Dipole | E = (1 / 4pi*E0) * (P/r^3) |

Eq. 5.10: Torque On A Dipole In An Electric Field | T = pE * sin(angle). E = magnitude of the uniform external electric field. |

Eq. 5.11: Magnetic Field From A Straight Wire | B = u0*I / 2pi*r. B = magnetic field at a distance, r, from the write. U0 is the permeability of free space: 4pi * 10^-7 T*m / A. I = current |

Eq. 5.12 Magnetic Field From A Loop Of Wire | B = u0I / 2r |

Eq. 5.13 Magnetic Force On A Moving Point charge | FB = qvB * sin(angle). q = charge, v = mag. of velocity, B = mag of magnetic field, angle = smallest angle between vector v and the magnetic field vector B. |

Eq. 5.14 Magnetic Force On A Current-Carrying Wire | FB = ILB * sin(angle). I = current, L = length of wire, B = mag of magnetic field, angle = angle between L and B. |

Created by:
SamB91