Unformatted text preview: Some Equations for Exam 2 tan = sin / cos ; sin2 + cos2 = 1. 1/2; cos 30 = 3/2; tan 30 = 3. 1/ sin 30 = sin 60 = 3/2; cos 60 = 1/2; tan 60 = 3. Some constants: c = 3 108 m/s; e = 1.602 10-19 C; 0 = 4 10-7 Tm/A; Lorentz force: F = qE + qv B. Ampere's Law: B ds = 0 i.
0 i 2r . 0 = 8.854 10-12 C2 /N m2 ; For an infinite straight wire: B = Faraday's Law: emf = - dB , where B = B dA is the magnetic flux. Lenz Law: dt the induced current in a closed conducting loop will be in the direction to oppose the change that produced it. The Biot-Savart law: B = dB =
0 4 i dsr r3 , The force acting on a wire element in a magnetic field: dF = i dL B. For a capacitor, q = CV. The energy U stored in a capacitor is U = 1 CV 2 . 2 Ohm's Law: R=V/I = const. For a parallel-plate capacitor (no dielectric), C = The capacitance of n capacitors in parallel: Ceq = The resistance of n resistors in series: Req =
0 A/d. With dielectric, C = in series:
1 Req 1 Ceq 0 e A/d. n 1 i=1 Ci . n i=1 Ci ; = n i=1 Ri ; in parallel: = n 1 i=1 Ri . V2 R . For a resistor, V = iR. Power dissipated in a resistor is P = iV = i2 R = In an RC circuit, capacitive time constant is C = RC. In an LR circuit, the inductive time constant is L = L/R. The reactance of a capacitor is XC = 1/C. The reactance of an inductor is XL = L. The impedance of a series LCR circuit is Z = R2 + (XL - XC )2 . Resonance angular frequency 2 = 1/LC. For EM waves in vacuum, E/B = c. Wavelength and frequency are related by c = f . 1 The direction of the wave is along the Poynting vector S = 0 E B. Intensity of polarized light through polarizer at angle with respect to light's polarization direction: I = I0 cos2 . 1 ...
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- Spring '08
- Force, Magnetic Field, Ri, 108 m/s, infinite straight wire, resonance angular frequency