Physics 222 3/20/03 name________________________

KE = 1/2 mv², F= ma , v² - v_o² = 2ax, v = v_o - at, x = v_ot+1/2at², a_c=v_T²/r

k = 1/4pe_o = 9x10⁹ Nm²/C² m_o = 4p x10^-7 Tm/A

1) Suppose the back of the room is at an electric potential that is 100V higher than the front of the room and the distance from back to front is 15m. The electric field in the room is uniform.

a) Which way would a proton fall in this potential (ignore gravity)?

b) Which way would an electron fall in this potential (ignore gravity)?

d) How much work would be done on one coulomb of charge if we move it from the front of the room to the back?

e) How much kinetic energy would a one coulomb charge have if it fell from the back to the front?

f) How much work would be done on one coulomb of charge in moving from the left wall to a point the same distance from the front on the right wall? Explain.

2) A nuclear accident creates a pulse of magnetic field which goes from 0 to 2000 T in 0.01 s. What Emf is induced in a TV antenna which consists of a single circular loop of wire with radius 15 cm?

3) In the jumping ring demonstration in class the solenoid has 200 loops per 10 cm of length and a diameter of 5cm. Suppose a current of I = 5 cos (2pft) amperes flows with f = 60 Hz and the coil has air in the center.

a) Use the fact that B = m_o n I to find the magnetic field in the solenoid as a function of time.

b) Find the emf in the ring as a function of time if it has a diameter of 5 cm (the same as the solenoid diameter so that the entire area has magnetic field through it).

c) What would you have to change in your answer to a and b in order to account for the fact that the solenoid is actually filled with iron, a ferromagnetic material?

d) If you are looking down on the solenoid while the current is flowing clockwise, which way does the induced current in the ring flow?

4) As the spaceship Voyager neared Jupiter a radio signal (f = 10⁸ Hz) was sent to it to turn on its TV cameras.

a) What is the wavelength of this signal?

b) If Jupiter is 630x10⁶ km away, how long does it take for the signal to get there?

5) Suppose the amplitude of the twisting of torsional waves on a slinky are given by the formula q(x, t) = 0.2 sin ( 2 x - 450 t ) where q(x, t) is the amount of twist measured in radians in the slinky at location x and time t.

a) What is the maximum displacement amplitude of the slinky from equilibrium (in radians)?

b) What is the frequency (in Hertz) of this torsional wave?

c) What is the speed of this torsional wave?

d) What is the wavelength of this torsional wave?

e) What is the angular velocity (in radians per second) of the slinky as a function of location and time (hint: this is NOT the speed of the wave)?

Bonus:

a) Explain how a CD gives different colors.

b) Explain the angle of resolution in the case of diffraction?

c) What is an eddy current? (and give an example.)