Survey

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Electrification wikipedia, lookup

Mains electricity wikipedia, lookup

Electric machine wikipedia, lookup

History of electric power transmission wikipedia, lookup

Electrical resistivity and conductivity wikipedia, lookup

Opto-isolator wikipedia, lookup

Alternating current wikipedia, lookup

Stray voltage wikipedia, lookup

Earthing system wikipedia, lookup

Electrostatics wikipedia, lookup

Electric charge wikipedia, lookup

Electrical resistance and conductance wikipedia, lookup

Wireless power transfer wikipedia, lookup

Superconductivity wikipedia, lookup

Electromagnetism wikipedia, lookup

History of electromagnetic theory wikipedia, lookup

Scanning SQUID microscope wikipedia, lookup

Electric current wikipedia, lookup

Eddy current wikipedia, lookup

Magnetohydrodynamics wikipedia, lookup

History of electrochemistry wikipedia, lookup

Electromotive force wikipedia, lookup

General Electric wikipedia, lookup

Insulator (electricity) wikipedia, lookup

High voltage wikipedia, lookup

Electroactive polymers wikipedia, lookup

Geomagnetic storm wikipedia, lookup

Transcript

Winter wk 3 – Thus.20.Jan.05 • • • • Ch.24: Voltage and electric field Ch.26: Current and resistance Solar applications Ch.27: Circuits Energy Systems, EJZ Equipotential surfaces and E fields Equipotential = constant voltage Conductors are equipotentials, in electrostatics Potential difference Electric field dV/dx = -E or, equivalently, V E dr Practice: Ch.24 Q5,8 (p.646), P#3, 4, 6, 35 Ch.24 #4 Ch.24 #6 Ch.24 #35 Electrostatics (d/dt=0): charges fields forces, energy E.dA = q/0=, E = F/q V (r ) 1 (r ' ) 4 d ' E dl E V F=qE=ma W = qV, C = q/V • Charges make E fields and forces • charges make scalar potential differences dV • E can be found from V • Electric forces move charges • Electric fields store energy (capacitance) Ch.26: Currents and Resistance Current = rate of flow of charge I = dq/dt Units: amps = coulombs/sec Current density: J = current/area = n e v Ch.26 Q1, 2, P.1, 8 Water flow: pressure volume/time Electricity flow: voltage V current I Ch.26: Q1, 2, P.1, 8 Resistance Resistance = resistivity * area/length R = * A/L Which conductor has the greatest resistivity? Ch.26: Q3 Ohm’s law In many substances, for a given resistance R, the stronger the driving voltage, the greater the current that flows: Voltage = current * resistance V=I*R Ch.26 Q5, P.17 Power in electric circuits Power = rate of energy xfr = voltage*current P=VI units: Watts = volts * amps Recall that work = qV. Units: J = CV Solve for V(J,C) = Then [volts]*[amps] = ____*C/s = ______ If V=IR, find P(I,R) = Ch.26 #35, 64 P(R,V) = Ch.27: Circuits: Battery pumps electricity current flows http://hyperphysics.phy-astr.gsu.edu/hbase/electric/watcir.html#c1 Voltage = emf Voltage = potential difference Electromotive force = V = dW/dq =work done per unit charge d/dx = -E = electric field Emf and electric field E d/dx = -E = electric field Using the fundamental theorem of calculus, we can derive another of Maxwell’s eqns: d E dx d dx dx E dx E dx Ch.27: Practice with simple circuits Q2 #5, 14 Solar applications Storms from the Sun: p.13: If a CME travels at 1 million miles per hour, how long does it take to reach Earth? p.16: The 2 May 1994 event dumped 4600 GW-hr of electricity into Earth’s upper atmosphere. How much energy is that in Joules? p.16: If the Earth’s mean magnetic field is B0=0.5 Gauss, and one Tesla=104 Gauss, by what percent does 2000 nanoTesla change Earth’s field? p.54: For the CME of 1 Sept 1859: calculate its speed v, if it took 18 hours to reach Earth. more Solar applications Storms from the Sun: p.77: If Rsun = 100 REarth, then find the ratio of their volumes, Vsun/VEarth p.77: If m=5 millions tons of mass is converted to energy (E=mc2) each second, calculate the power (P) produced by the Sun. p.82: If the Sun’s mass is M=2x1030 kg, and it keeps losing dm/dt = 5 million tons per second, how long (T) can the Sun last? p.83: If the solar wind pours I=1 million amps into Earths magnetosphere, how much charge (Q) is that per day? Extra solar applications p.13: Calculate vthermal from Tsolar wind. Compare to vflow. p.16: Derive the altitude for a geosynchronous orbit p.77: If the Sun’s core temperature is about T=107K, calculate the thermal speed vth of protons in the core.