A carpenter uses sandpaper on a piece of wood. Before, the wood felt rough. After, the wood felt smooth. Did the friction between the hand and the wood increase or decrease after using the sandpaper?

Suppose that an electromagnetic wave which is linearly polarized along the x−axis is propagating in vacuum along the z−axis. the wave is incident on a conductor which is placed at z > 0 region of the space. the conductor has conductivity σ, magnetic permeability µ and electric permittivity ε. (a) find the characteristic time for the free charge density which dissipates at the conductor. (b) write the maxwell equations and derive the wave equation for a plane wave propagating in a conductor. (c) find the attenuation distance at which the incident amplitude reduces to e ^−1 of its initial value. (d) find the electric and magnetic fields inside the conductor. 8 (e) find the power loss per area of the incident electromagnetic wave at the surface of conductor.

An electron moving at 5.06 103 m/s in a 1.23 t magnetic field experiences a magnetic force of 1.40 10-16 n. what angle does the velocity of the electron make with the magnetic field? there are two answers between 0° and 180°. (enter your answers from smallest to largest.)

Which of the following is the largest disadvantage of about half of the electricity in the united states comes from burning