Cheat Sheet for Final Exam - General Physics | PHYS 2206, Study notes of Physics

Download Cheat Sheet for Final Exam - General Physics | PHYS 2206 and more Study notes Physics in PDF only on Docsity! Chapter 12: Temperature and Heat • Heat and internal energy Energy that flows from a higher temp object to a lower temp object b/c of the diff in temp (object can’t contain heat) Internal energy is the sum total of all energy of all the molecules in an object. U2/m2 = U1/m1 • Specific heat capacity Q = cmΔT <c> J/kgC Ui+Q=Uf cwater=4186 • Calorimetry. Measuring the specific heat capacity Qlost=Qgained calorimeter measures an isolated system • Heat and phase changes. Latent heat Q=Lm fusion: liquid to solid…vap: liquid to gas Chapter 13: The Transfer of Heat • Convection-process in which heat is carried from place to place by the bulk movement of a fluid (only liquids and gases) Convection current-what drives the transfer of heat Natural-occurs b/c of a difference in temp which causes a current to form forced convection-external device mixes the warmer and cooler portions of a fluid or air • Conduction-process in which heat is transferred directly through a material with any bulk motion playing no role in the transfer Conduction through a material. Q = kAΔT/L <k> J/smC (material constant and thermal conductivity) Q/t = kAΔT/L <Q/t> watts  J/s  heat current • Radiation-process in which heat is transferred by means of EM waves **does not require a material medium to transfer heat Perfect blackbody-emits as much as it absorbs The Stefan-Boltzmann law- Q/t = σAT4 ::T in Kelvins σ = 5.67E -8 <E -8 <σ> J/sm2K4 if not a blackbody: Q/t = eσAT4 ::e is emissivity Net Radiant Power is simly subtracting the initial from the final Q/t values Chapter 14: The Ideal Gas Law and Kinetic Theory • Atomic mass unit- 1 u = 1.6605E -27E -8 < kg (size of one proton) Avogadro’s number (NA= 6.022E 23 mol-1 N vs. n:: N # of molecules…n is # of moles M vs. m:: M is Molar mass…m is simply mass n=N/NA • Ideal gas law-molecules move in straight lines with only elastic collisions and there are no interactions PV = nRT PV=nNAKBT or PV=NKBT R (Universal gas constant) = 8.3145 J/molK KB = R/NA = 1.38E -23 J/K T in Kelvin and P must be in absolute pressure (atm = 1.013E 5 Pa) • Internal energy of a monoatomic ideal gas- Maxwell distribution where hump is most likely speed (P=F/A) PV = 2/3N(KE) KE = 3/2KBT U = 3/2nRT Chapter 15: Thermodynamics • Adiabatic-does not allow the passage of heat into the system diathermal-allows heat to flow through • Thermal equilibrium. The zeroth law of thermodynamics -two systems are at thermal equilibrium if there is no heat flow between them—both systems are at the same temp therefore the 3rd system is also in equilibrium • The first law of thermodynamics. Signs for heat and work- Q is positive when heat is transferred into the system and is negative when heat is flowing out of the system W is positive when it is done by the system on the surroundings and negative when it is done on the system by the surroundings. ΔU = Q – W Q = ΔU + W • Heat, work and the first law P1V1/T1 = P2V2/T2 in closed systems isobaric- pressure always constant W = P ΔΔV ΔU = 3/2nR ΔΔT  Q = W + ΔU V1/T1 = V2/T2 V1V2 + W and V2V1 –W isochoric- volume always constant ΔV = 0  W= 0 Q = ΔU + 0  W = 3/2nR ΔΔT P1/T1 = P2/T2 isothermal- temperature stays constant P1V1=P2V2 W = nRTln(V2/V1) or (P1/P2) W = PVln(V2/V1) or (P1/P2) V1V2 + W and V2V1 –W and same for P ΔU = 0 b/c only depends on Temperature Q = W (blowing into your hands to warm them up is a good example of this) adiabatic- no heat transfer Q = 0 P1V1γ = P2V2γ γ is the Adiabatic exponent ΔU + W = 0  ΔU = -W ΔU = 3/2nR(Tf – Ti) and W = 3/2nR(Ti – Tf) | (-ΔT) blowing on your coffee is a good ex b/c there is no time for the air to heat up • Molar specific heat Q = Cm ΔΔT <C> J/molC (specific heat) Specific heat at constant pressure Qp = 5/2nR ΔΔT Cp = 5/2R and at constant volume Qv = 3/2nRΔT Cv = 3/2R Cp/Cv = γ • The second law of thermodynamics -heat flows spontaneously from a substance of higher temp to a substance of lower temp and does not flow spontaneously in the reverse direction • Heat engines (W, QH, QC) QH = W + QC Efficiency:: e = W/QH e = QH – QC/ QH  e = 1 – QC/QH Carnot’s principle- if all the processes are perfectly reversible, then the engine will have its maximum efficiency and bringing both system and surroundings from final state back to initial state is perfectly reversible--- all Carnot engines operating between the same two temps will have the same efficiency, irrespective of the nature of the working substance The Carnot engine QC/QH = TC/TH ecarnot = 1 – TC/TH • Entropy: measure of disorder The second law of thermodynamics:: the total entropy of any system PLUS that of its environment increases as a result of any natural process and best you can achieve is a zero change in entropy being 0 so always a net increase ΔS = Q/T <S> J/K • The third law of thermodynamics- it is not possible to lower the temperature of any system to absolute zero (0 K) in a finite number of steps Chapter 18: Electric Forces and Electric Fields • Coulomb’s law- e = 1.60E -19 C magnitude of p and e F = kq1q2/r2 <k> 8.99E 9 Nm2/C2 • Electric field & electric field lines. F/q0 = kQ/r2 E = F/q0 <N/C> F = q0E • The field inside the parallel-plate capacitor -the field in between two plates are uniform meaning the distance doesn’t matter E = σ/ε0 E = (Q/A)/ε0 <ε> 8.854E -12 E/m “electric permittivity of free space” <σ> Q/A C/m2 Chapter 19: Electric Potential Energy and the Electric Potential • Work as difference in potential energy. Electric potential energy -WA:B = UA – UB where U = EPE (J) depends on the displacement and magnitude of the charge F/qo = kQ/r2 • Electric potential and its relationship with the electric potential energy. V = U/qo or U = qoV electric potential— energy per unit charge Work in terms of ΔV V W = qoΔV and ΔKE = Wnet • Potential of a point charge. Potential difference created by point charges WA:B/qo = kQ/ra – kQ/rb V = kQ/r • Equipotential surfaces and their relation to the electric field WA:B = qo(VA – VB) -it takes zero work to move a charge on an equipotential surface and always from high V to low V E = ΔV V/ ΔV x V/m = N/C -the electric field E is always perpendicular to equipotential surfaces and points in the direction of decreasing potential -if E = 0 at all points, such as inside a conductor in electrostatic equilibrium, then the potential difference between any two points is ΔV V = 0 • Capacitance defined. -a capacitor is a container for charges Q = CV or C = q/V <C> = Farad (F) Capacitance of a parallel plate capacitor. C = ε0A/d Energy stored in a capacitor. U = CV2/2 = q2/2C = qV/2 Energy density u = ε0E2/2 <u> = J/m3 u = U/volume = U/Ad Chapter 20: Electric Circuits • emf- the maximum potential difference of the battery in the outside circuit, the e- go to the p+ I = ΔV q/ ΔΔV t <I> C/s = ampere (A) • Ohm’s law - R is not a material constant…the characteristics of the wire makes a difference V = RI or R = V/I R is resistance <R> Volt/Ampere or Ohm Ω • Resistance & resistivity R = ρ(L/A) <resistivity> Ωm • Electric power U = V ΔV q P = U/ ΔV t P = IV P = I2R P=V2/R • Resistors in series- same current, voltages will be different but add up to total Rs = R1 + R2 + … and in parallel- same potentials (V), but currents are not the same, but add up to total 1/Rp = 1/R1 + 1/R2 + … **for 2 resistors: (R1R2)/(R1+R2) = Rp Equivalent resistance • Internal resistance of a real battery. VB – VA = V0 – IR • Finding potential differences. The emf and resistance rules -for a move through a resistor in the direction of the current, the change in potential is –IR -opposite direction it is +IR -current flows in direction of decreasing potential -for a move through an ideal emf from – to +, the change in potential is +ε , the opposite direction is –ε • Kirchhoff’s junction -the total current in a junction directed into a junction must be equal to the total current directed out of the junction -and loop rules the algebraic sum of the changes in potential around a closed loop of a circuit is zero • Capacitors in series C = Q/V same charge, potentials add up, Q1=Q2=Qtot 1/Cs = 1/C1 + 1/C2 + … and in parallel. same voltage, charges add up C1 + C2 = Cp • RC circuits. Capacitor charging Q = Q0 [1 – e^-t/RC] & discharging. Q = Q0e^-t/RC Time constant. τ = RC Ω(F) = seconds Steady state (equilibrium) values for the charge and current VR= IR Vc=Q/C steady-state- current = 0, VR = 0, Vc = V0 Q0 = cV0, t = 0, charge = 0, t = ∞, charge = Q0 Vc = V0 [1 – e^-t/RC] I = I0e^-t/RC t = 0, I = Io, t= ∞, I = 0 Chapter 21: Magnetic Forces and Magnetic Fields • The force exerted by the magnetic field on a moving charge. –Lorentz Force The first right-hand rule---it’s for a positive charge Definition of B in terms of the force FB = qVBsin() • The motion of a charge in a magnetic field. 2 conditions for a charge to experience a magnetic force when placed in a magnetic field: 1..the charge must be moving 2..the velocity of the moving charge must have a component perpendicular to the magnetic field B = FB/qvsing() Comparison with the electric field. FE = qE and FB = qVBsin() electric field has a parabolic trajectory magnetic field moves upward when going north to south The work done on a charge moving through electric and magnetic fields -Fb = mv^2/R R = mv/qB • The force on a current in a magnetic field