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Describe the shape/direction of electric field lines
 They radiate outward from + charges and toward  charges (test charge is +)
 They form various shapes if they are near eachother

What does "F_{12}" mean?
The force that 1 exerts on 2 (look at it from 2's perspective)

tan/sin/cos?
 tan = opp/adj
 sin = opp/hyp
 cos = adj/hyp

Other useful equations to remember regarding force?
 F=ma
 F=mv^{2}/r (circular motion)

Describe electric potential of charges in a parallel plate capacitor
charges move from + to  therefore charges that are closer to the + plate have increased potential energy

How do you determine the potential energy of a group of charges? (a system)
Detrmine the potential energy (Vq = kq1q2/r) for each point and then sum them. Easy.

How do you determine the difference in energy of something between 2 plates?
 KE + PE = KE + PE
 If stopped, KE=0
 If at the  plate, PE = 0

Describe the equivalent properties (q,V,C) for a capacitor in series. A resistor? (R, I)
 q_{eq}=q1=q2=q3
 V=V1+V2+V3
 1/C_{eq}=1/C1+1/C2+1/C3
 R_{eq}=R1+R2+R3
 I=I1=I2=I3

Describe the equivalent properties (q,V,C) for a capacitor in parallel. A resistor? (R,I)
 q=q1+q2+q3
 V=V1=V2=V3
 C=C1+C2+C3
 1/R_{eq} = 1/R1+1/R2+1/R3
 I=I1+I2+I3

Describe Kirchoff's point rule.
The sum of current into a junction is equal to the sum of the current out of a junction

How do you perform Kirchoff's loop rule?
 1. Choose a direction for I
 2. Choose a start point
 3. Move along the circuit in a direction, moving back toward point chosen in step 2
 4. Use rules for crossing various elements and place into equation
 5. Apply loop rule
 6. Solve for the unknown

What is internal resistance?
The resistance WITHIN a battery (should be obvious)

Magnetic field direction?
Flows from north and into south

 eq1 = long straight wire carrying a current, causing circular magnetic field around it
 eq2 = loop carrying a current, causing straight magnetic field through center (a=radius of loop)
 eq3 = solenoid carrying a current, causing straight magnetic field through center (n = #turns/unit length)

symbols for into vs out of page (magnetic field)
x is into and o is out of

What are the various "right hand rules"
 For current in a loop: thumb aligns with current and fingers curve to show direction of B field
 For wire in a B field: I(thumb) B(index) F(middle)
 For charged particle in a B field: v(thumb) B(index) F(middle)
 ***remember if charge is negative then reverse direction!

What is the equation for the force of a circular object?

What are the two types of mechanical waves (direction)
 Transverse: the element moves vertically white the velocity is horizontal
 Longitudinal: the element AND velocity move only horizontally

What are the characteristics of a wave?
 frequency (f): # oscillations per second
 wave length (λ): distance wave travels before it repeats
 Period (t): time it takes for one cycle to be completed
 f=1/t

Difference between electromagnetic waves and mechanical waves?
EM waves do not need a medium to travel

Wave front vs ray? What is their relationship?
 Wave front: the wave itself (the ripple after throwing a stone)
 Ray: the direction that the wave travels
 Wavefronts and rays are always perpendicular

Describe the laws of reflection, refraction, and diffraction
 *remember all angles taken between ray and NORMAL of surface
 reflection: Angle of incidence = angle of reflection
 Law of refraction: angle of incidence > angle of refraction
 ray refracts TOWARD the normal

What is the critical angle?
 When the angle of refraction becomes 90 degrees
 Anything above is total internal reflection

Describe the reflections of a concave mirror
 a ray parallel to the principal axis is reflected through F
 a ray that pass through F is reflected parallel to the principal axis
 a ray that meets the mirror at the principal axis is reflected at the same angle
 a ray that passes through O is reflected directly back (180)

What makes an image real, inverted, larger, smaller, etc in a reflection?
 real/virtual: if the light meets in front of the mirror it is a real image
 inverted/upright: if the light meets on the opposite side of the principal axis then it is projected from it is inverted
 larger/smaller: if the light meets at a point PAST the source then it is larger

Describe the light passthrough in a converging lens
 ()
 Ray parallel to principal axis passes through focal point on other side
 Ray passing through principal axis in center of lens continues without refraction (0 change)
 Ray passing through focal point continues straight on other side

Describe light passthrough in a diverging lens
 )(
 Ray parallel to principal axis refracts away from the principal axis so that an imaginary line from the focal point is straight
 Ray passing through principal axis in center of lens continues without refraction
 Ray aimed at opposite side F (imaginary line) will come out parallel to principal axis

