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# MCAT Physics Ch. 6

Term | Definition |
---|---|

Current | Movement of charge that occurs between two points that have different electrical potentials. Negatively charged particles (electrons) move in a circuit from low potential to high potential. |

Current Flows Only In: | Conductive materials. |

Metallic Conduction Relies On: | Uniform movement of free electrons in metallic bonds |

Electrolytic Conduction Relies On: | Ion conc. of a solution |

Insulators | Materials that do not conduct a current |

Kirchhoff's Laws | Express conservation of charge and energy |

Kirchhoff's Junction Rule | States that the sum of currents directed into a point within a circuit equals the sum of the currents directed away from that point |

Kirchhoff's Loop Rule | States that in a closed loop, the sum of voltage sources is always equal to the sum of voltage drops |

Resistance | Opposition to the movement of electrons through a material. |

Resistors | Conductive materials with a moderate amount of resistance that slow down electrons without stopping them. |

Ohm's Law States That: | For a given resistance, the magnitude of the current through a resistor is proportional to the voltage drop across the resistor |

Resistors In Series Are: | Additive and sum together to create the total resistance of a circuit |

Resistors In Parallel Cause: | A decrease in equivalent resistance of a circuit. |

Capacitors Have The Ability To: | Store and discharge electrical potential energy |

Parallel Plate Capacitors' Capacitance Is Determined By: | The area of the plates and the distance between the plates. |

Capacitors In Series Cause A: | Decrease in the equivalent capacitance of a circuit. |

Capacitors In Parallel: | Sum together to create a larger equivalent capacitance. |

Dielectric Materials | Insulators placed between the plates of a capacitor that increase the capacitance of the capacitor by a factor equal to the material's dielectric constant, k |

Ammeters Are Inserted In Series In A Circuit To: | Measure current since they negligible resistance |

Voltmeters Are Inserted In Parallel In A Circuit To Measure: | A voltage drop, since they have very large resistances |

Ohmmeters Are Inserted Around A: | Resistive element to measure resistance, since they are self-powered and have negligible resistance. |

Eq. 6.1: Current | I = Q / Delta T. Q = charge. |

Eq. 6.2: Kirchhoff's Junction Rule | I intojunction = I leaving junction. I = current. |

Eq. 6.3: Kirchhoff's Loop Rule | Vsource = Vdrop. V = voltage. |

Eq. 6.4: Definition Of Resistance | R = d*L / A. d = resistivity. L = length of the resistor. A = cross-sectional area. |

Eq. 6.5: Ohm' Law | V = IR. V = voltage. I = Current. R = resistance. |

Eq. 6.6: Voltage And Cell emf | V = Ecell - i*r(int). Ecell = emf of cell. i = current through cell. r(int) = internal resistance. |

Eq. 6.7: Definition Of Power | P = W / t = Delta E / t. Delta E = change in emf. |

Eq. 6.8: Electric Power | P = IV = I^2 * R = V^2 / R. I = current. R = resistance. V = voltage. |

Eq. 6.9: Voltage Drop Across Circuit Elements (Series) | Vs = V1 + V2 + V3 +...+ Vn |

Eq. 6.10: Equivalent Resistance Series | Rs = R1 + R2 + R3 + ... + Rn |

Eq. 6.11: Voltage Drop Across Circuit Elements (Parallel) | Vp = V1 = V2 = V3 = ... = Vn |

Eq. 6.12: Equivalent Resistance (Parallel) | 1 / Rp = 1 / R1 + 1 / R2 + 1 / R3 + ... + 1 / Rn |

Eq. 6.13: Definition Of Capacitance | C = Q/V. Q = charge. V = voltage. |

Eq. 6.14: Capacitance Based On Parallel Plate Geometry | C = E0 (A / d). E0 = permittivity of free space, 8.85 x 10^-12 F/m. A = area of overlap of two plates. d = separation of two plates. |

Eq. 6.15: Electric Field In A Capacitor | E = V / d. V = voltage. d = distance between two plates. |

Eq. 6.16: Potential Energy Of A Capacitor: | U = 1/2 * CV^2. C = capacitance. V = voltage. |

Eq. 6.17: Capacitance With A Dielectric Material | C^1 = kC. k = dielectric constant, the measure of a material's insulating ability. C = capacitance. |

Eq. 6.18: Equivalent Capacitance (Series) | 1 / Cs = 1 / C1 + 1 / C2 + 1 / C3 + ... + 1 / Cn |

Eq. 6.19: Equivalent Capacitance (Parallel) | Cp = C1 + C2 + C3 + ... + Cn |