Outline Overview/Mind-map What each equation does Practice Problems
Sorry about the boring theme. I couldn’t find a suitable theme that I liked, that didn’t mess up my text. However, looking at green is said to increase creativity and stimulate brain function. May use this later.
Electric field lines go from + to -. Also, line density indicates field strength
Dipole moment, BY DEFINITION Notice: Dipole moment points from negative to positive….opposite of the direction E points
Torque on a dipole by the external electric field – Note that E is not the E produced by the dipole – E is external Torque is maximum when dipole moment and E are perpendicular.
Potential energy is minimum (also called stable equilibrium) when two things are true: – Dipole moment is parallel to E – Dipole moment points in the same direction as E. Potential energy is maximum (also called unstable equilibrium) when two things are true: – Dipole moment is parallel to E. – Dipole moment points in the opposite direction as E.
Also known as Gauss’s Law Really there are two equations here…but they’re both equally valid…always.
Steps in solving Gauss’s Law Problems – Draw a picture of the object. Pick a good Gaussian surface. – Write down the expression of Gauss’s Law that involves the dot product between E and A. (If E is perpendicular to A, the flux is 0 for that surface. Otherwise, use symmetry to get rid of the integral.) – Write down the expression of Gauss’s Law that involves the total charge q. – Set the two expressions equal to each other and eliminate variables.
This one is especially important. This is the electric field anywhere away from a large sheet of charge. Notice that the electric field doesn’t depend on distance, and always points perpendicular to the surface.
This is the defining relation between potential energy (U) and electric potential (V). Note: since q 0 can be positive or negative, U and V do not necessarily have the same sign. One more time: Electric potential (V) is not the same thing as electric potential energy (U) But let’s rewrite it.
In the figure to the right, there are two charges connected by a massless insulating rod…and remember to use VECTORS when appropriate… Draw the electric dipole. Torque caused by the electric field= Dipole moment= Potential energy as it is right now= Which way will the dipole begin to rotate? (Clockwise/Counter-clockwise) How much work is done in rotating the dipole from its current position to the stable equilibrium position? What does the work in question f?
A block of MagicFoam (length 10 cm, width 10 cm, height 3 cm) sits on top of a calm body of water. MagiFoam density=0.5 g/cm 3. How much of the block is submerged? A 10 kg block floats in the water. What is the buoyant force on it? A house with a roof of area 5 m 2 has winds of 50 m/s above it. What is the force on the roof caused by the pressure difference?