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UMass Amherst PHYSICS 132 - 132 final guide

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1kHz=1000Hz e=1.6E-19 Hz=kHz*1000 1 cm=.01 m Hz=mHz*1000000 1 A=1000mA Speed(v)=c/n Time taken=d/v c=3E8 m/s d=thickness’ Ex. dg= 5 cm thick layer of oil n=1.46 wedged between dg=1 cm thick sheet of glass n=1.5 and dp=2 cm thick sheet of polystyrene n=1.59 How long does it take the light? Vg=3E8/1.5=2E8 tg=.01m/2E8=.050E-9 Seconds V0=3E8/1.46=2.05E8 TO= .05/2.05E8=.243E-9 s Vp=3E8/1.59= 1.8867E8 Tp=.02/1.8867E9=.1060E-9 .05ns+.2433ns+.1060 ns=.399ns Wavelength=2*n*d/m (or m+.05???) m=1 (for thinnest sheet) d=thickness c=Wavelength*frequency Compared to the average speed in the air the average speed of a beam of light in glass is less Electromagnetic waves can travel through either a medium or a vacuum Colors seen when gasoline forms a thin film in water are an example of interference The critical angle for a transparent material is the angel at and beyond all light within the material is reflected Critical angle is less in a diamond Snell's Law=n1sin()=n2sin() Virtual:Upright and small Real=Flipped Position of an image=1/do+1/di=1/f f=Focal length do=object position di=Image position Sin()=n1/n2 Ex. The index of refraction of the core of a piece of fiber optics cable is 1.72. Surrounding=1.41 What is the critical angle? Sin()=1.47/1.72 Angle=58.7 Slit spacing= Wavelength*distance to screen/distance between fridges Bright bands=1,2,3,4 Dark Bands=1.5,2.5,3.5,4.5 Distance from central spot to nth order fridge=m*L*R/d L=wavelength R=distance from slit to screen dsin()=m*L An erect object is 50cm from a concave mirror of radius 60 cm . In this situation the character of the image is? 1/30=1/50+1/q q=75 Since q is positive image is real Magnification=-q/p -75/50=-1.5e A hydrogen nucleus +e, is situated left of a carbon nucleus +6e. The electric force experienced by H is equal to the left and the magnitude is equal to the force exerted on C Which represents the net force B If two objects are electrically attached to each other the Objects could be electrically neutral A plastic rod is charged up + and brought to a neutral sphere. After they separate the rod is repelled by the sphere Forces are equal How many electrons are needed to produce 1.0 of negative charge? e=1.60 (1)*1/e 1*(1/1.60)=6.3E18 F1=kq1q2/r^2 q=6.7 Nc K=1/4piE0=9.0E9 9.0E9*6.7E-9*2E-9/(.01m)^2=1.206E^-3=F1,F2 Fnet=F1*cos(30)*F2*cos(30)=2.088E-3N E=kQsource/r^2 If you were to cut up a small permanent magnet bar in half each piece would be a magnet with a north and south pole1kHz=1000Hz e=1.6E-19 Hz=kHz*1000 1 cm=.01 m Hz=mHz*1000000 1 A=1000mA An electron is moving to the right encounters a uniform magnetic field pointing out of the page E would move up A charged particle that is moving in a static uniform magnetic field may experience a magnetic force but its speed wont change An electron, moving west, enters a magnetic field. Because of this field the electron curves upward. We may conclude that the magnetic field must have a component: towards the north Two equal and opposite charges are a small distance apart, forming an electric dipole. A positive charge +q is placed above these charges, as shown in the figure, equidistant from both of them. Which diagram below best gives the direction of the net force the dipole exerts on the charge +q? ______> Increasing flux: The induced magnetic field points opposite the applied magnetic field. Decreasing flux: The induced magnetic field points in the same direction as the applied magnetic field. Steady flux: There is no induced magnetic field. Lenz's law states that when an emf is generated by a change in magnetic flux according to Faraday's Law, the polarity of the induced emf is such, that it produces an current that's magnetic field opposes the change which produces it. 1. Charge: Positive negative and neutral charges a. Units=Coulombs © 2. Current I=Q/t a. Amount of charge that travels in a given time b. Unit=Amp (Coulomb/sec 3. Voltage: Energy per unit charge a. Unit=Volts=Joules/Coulomb) 4. Resistor: Resistance a. Units=Ohms (Ω) 5. Power Ohm’s Law V=I*R Combinations 1.Series: Two resistors side by side ● Will have effective resistance. R1+R2=effective 2. Parallel: Two resistors parallel to one another ● 1/R effective=1/R1 +1/R2 Current passes through a solution of sodium chloride. In 1.00 second, 2.68×1016Na+ ions arrive at the negative electrode and 3.92×1016Cl− ions arrive at the positive electrode. Change in Na ions=q=ne=(2.6E16*1.69E-19)=4.288E-3C Change in Cl ions=q=n*e=(3.92E16*1.69E-19)=6.272E-3 Current=i=q1/t+q2/t=10.56E-3 A=10.56mA Charge=q=i*t I=current t=time Electrons flow=n=q/e A 3.0 [V] battery powers a flashlight bulb that has a resistance of 6.0 [O]. How much charge moves through the battery in 10 [min]? Voltage V=3.0 V Resistance R=6.0 Ohm Current I=V/R =3/6 =0.5 A Current =charge flow/time Charge Flow=current*time =0.5*10*60(As 10 minutes is 10*60 seconds) =300 C What is the voltage of a battery that will charge a 4.0 uc capacitor to +/-60 uc Q = C V ==> V = Q / C = 60.0 uC / 4.0 uF = 15 V Q=Charge C=Capacticity V=volts Work done=q(V1-V2) C=eoA/d


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UMass Amherst PHYSICS 132 - 132 final guide

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