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# Stack #39336

### Electrostatic/magnetic/dynamic formulas

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

What is the formula for the electrostatic force between 2 charges q1 and q2 separated by a distance r | F = k(q1)(q2)/(r^2) |

What is the formula for the force felt by a positive test charge (q) when brought into an electric field of strength E | F = qE |

What is the electric field (E) at a distance r away from a point charge Q? | E = KQ/r^2 |

What is the formula for the electric potential (V) due to a source charge Q at a distance r from the source charge? | V = KQ/r |

What is the formula for the potential difference (V) in measuring the work done to move a charge q against an electric field? | V = work/q |

What is the formula for the electric potential energy between 2 charges q1 and q2, initially at an infinite distance apart, to a separation distance of r? | U = K(q1)(q2)/r |

The electric field (E) between 2 plates d units apart with a voltage (V) across the plates is? | E = V/d |

A parallel plate capacitor has a capacitance (C), expressed in terms of area (A) and distance apart (d) of? | C = (permittivity)*A/d |

The electric energy (U) stored in a capacitor is? | U = 1/2 CV^2 or (1/2)QV |

Capacitors in parallel? | C = C1 + C2 + ... |

Capacitors in series? | 1/C = 1/C1 + 1/C2 + ... |

How does the electric field and charge quantitiy change when a dielectric is added to a capacitor? | E is decreased, but the amount of charge is increased. |

The resistance (R) of a wire is dependent upon the resistivity (rho), the length (l) and the cross-sectional area (A) as? | R = rho(l)/A |

Ohm's Law | V = IR |

Resistors in series? | R = R1 + R2 + ... |

Resistors in parallel? | 1/R = 1/R1 + 1/R2 + ... |

Units of magnetic field? | Tesla |

How does B vary with current and the distance from the current-carrying wire? | B=kI/r |

Force on a length L of a current (I)-carrying wire in a magnetic field B? | F = ILBsin(theta) |

Force on a charged (q) particle moving with velocity (v) through a magnetic field (B)? | F = qvBsin(theta) |

Undeflected motion of a particle through a magnetic field? | r = mv/qB |

Lorentz force (sum of electric and magnetic forces)? | qE = qvB or E=vB |

Faraday's Law | induced emf = change in flux/change in time |

Magnetic flux | = BA sin (theta) or Q(enclosed)/permittivity |

Induced current (I) | =-Blv/R |

Intensity of a sound wave= | power/area |

Transformer rule | Vp/Np=Vs/Ns or Power in primary side=Power in secondary side |

Velocity of sound wave= | freq * wavelength |

Doppler Effect= | app freq = freq (v + vo)/(v - vs) |

Snell's Law | n1*sin(theta1) = n2*sin(theta2) |