A step-up transformer is designed to have an output voltage of 2300 V (rms)
when the primary is connected across a 115-V (rnis) source. (a) If there are 100
turns on the primary winding, how many turns are required on the secondary?
a. 1000
GFnS
f4f73
=
B\r
= 20
(b) If a load resistor across the secondary draws a current of 1.5 A, what is the
current in the primary, assuming ideal conditions??
2. Calculate the minimum wavelength x-ray that can be produced when a target is
struck by an electron that has been accelerated through a potential difference of
25.0 kV?
e. 0.500 nrn
3. The period of a pendulum is 4.0 s in a stationary inertial frame of reference. What
is its period when measured by an observer moving at a speed of 0.60 c with
respect to the inertial frame of reference?
4. X-rays are Compton scattered from electrons in a carbon target. The measured
wavelength shift is 4.10 x 1o - nm.
~ What is the scattering angle of the x-rays?
5. An electromagnetic wave with a peak magnetic field component of 7.5 x 1o - ~T
T d A , a = 8.85 x 10-l2
carries what average power per unit area? (M = 4 n x 1o - ~
c 2 / N m 2and c = 3.00 x lo8 d s ) ?
6. A 20.0 pF capacitor and a 50.0 kR resistor are connected in series to a 5000 V ac
source with a frequency of 20.0 kHz. (a) What current flows through the resistor?
(b) What is the voltage across the resistor?
7. What is the average power dissipation in an RLC series circuit in which R = 20 0,
L = 0.1 H, and C = 10 pF dnven at resonance by a 100-V ( m s ) source?
8. What is the speed of a particle whose total energy is three times its rest energy?
9. Cesium metal has a work function of 1.90 eV. If violet light of wavelength 400
im illuminates the surface of the metal, what is the maximum kinetic energy of
the ejected electrons?
10. A torch is used to melt a sample of quartz whose melting temperature is 1925 K.
If the molten quartz radiates as a black body, what is the peak wavelength of the
light emitted by quartz?
11. Assuming the mass of an electron can be converted completely to energy, how
many electrons would have to be destroyed in order to run a 100 W lightbulb for
60 seconds? (Hint:
Watt = Joulelsec)
12. An astronaut in a spaceship travels at a speed of 0.8 c away from an observer at
rest on the Earth. He turns around and shines a beam of light toward the
stationary observer. What does the stationary observer measure for the speed of
the light beam (in vacuum)?