review. dc circuits resistors in series resistors in parallel
Post on 14-Dec-2015
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Junction Rule
At any junction point, the sum of all currents entering the junction must equal the sum of all currents leaving the junction.
Take the signs:
For A Resistor:
- IR if your chosen loop direction is the same as the chosen current direction.
+ IR if the directions of loop and current chosen are opposite.
For A Battery:
+ if your loop direction moves from the negative terminal to positive.
- if your loop direction moves from the positive terminal to negative.
Important difference: the isolation of a single magnetic pole seems impossible! So far there is no confirmation of existence of magnetic monopole.
Important: the direction of the force is always perpendicular to the direction of the current and also perpendicular to the direction of the magnetic field.
Faraday’s Law of Induction
If the flux through N loops of wire changes by the amount of B during time t, the average induced emf during this time is:
tN B
Lenz’s Law
An induced emf always creates a current whose magnetic field opposes the original change in flux.
The ratio of the speed of light in vacuum to the speed of light v in a given material is called the index of refraction, n of the material:
n=c/v
Important: total internal reflection can occur only when light strikes a boundary where the medium beyond has a lower index of refraction.
-ray 1 is drawn parallel to the axis; therefore it must pass along a line through F;
-ray 2 is drawn through F, as result is must reflect into parallel to the principal axis ray;
-ray 3 is chosen to be perpendicular to the mirror, and so is drawn so that it passes through C, the center of curvature; it will be reflected back on itself.
The lateral magnification, m, of a mirror is defined as the height of the image divided by the height of the object:
o
i
o
i
d
d
h
hm
The Sign Convention
-the image height hi is positive if the image is upright, and negative if inverted, relative to the object;
-di and do are both positive if image and object are on the reflecting side of mirror, but if either image or object are behind the mirror, the corresponding distance is negative.
-ray 1 is drawn parallel to the axis; therefore it is refracted by the lens so that is passes along a line through the focal point;
-ray 2 is drawn on a line passing the other focal point F’ and emerges from the parallel to the axis;
-ray 3 is directed toward the very center of the lens, this ray emerges from the lens at the same angle as it entered.
1. The focal length is positive for converging lens and negative for diverging.
2. The object distance is positive if it is on the opposite side of the lens from where the light is coming; otherwise it is negative.
3. The image distance is positive if it is on the opposite side of the lens from where light is coming.
4. The height of the image is positive if the image is upright and negative if the image is inverted relative to the object.
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