1. Calculate work done by expanding gas of 1 mole if initial pressure is 4000 Pa, initial volume is 0.2 m3.
Assume a two processes: (1) isobaric expansion to 0.3 m3 (2) isothermal expansion to 0.3 m3.
1. Isobaric expansion:
Also:
A 50% increase in temperature!

2. 2. Isothermal expansion:
Also:
A ~67% decrease in pressure!

3. An infinitely long wire, as shown in the figure, is uniformly charged with
density of λ. The radius of the ¼ circle is R. Find the electric field at O. O B A ∞ y
A ∞ θ θ x B∞ AB

4. Contribution from filled part:
A uniformly charged sphere (charge density of ρ) with a sphere hole inside is
shown in the figure. Find the electric field intensity at the center of the hole.
Filled: O r d
Contribution from filled part:

5. Two point charges (q and -2q) are located at x=1m and x=-1m, respectively.
Another point charge is located on the X axis. What is the position of this charge
so that the net electric force on it is zero?

6. Find the magnetic field intensity at P.
r =0.1 cm
30o
30o P

7. An electron is passing A with a speed of 104 m/s in a perpendicular magnetic field.
Find the radius of the electron’s circular motion and the frequency of the cyclotron.
frequency

8. A straight long wire with current I is placed beside a metallic trapezoid . ab=bc=ad=L. Distance between point d and the wire is l. The trapezoid freely falls a height H from still.
Find 1) the instant induced current in the trapezoid when it falls H.
2) the potential difference between dc at that moment.
60o

9. A setup of double-slit interference is shown below. D=1. 2m, d=0. 45mm
A setup of double-slit interference is shown below. D=1.2m, d=0.45mm. If the
distance between adjacent bright lines on the screen is 1.5mm. Find the wavelength
of the source light. P D △x

10. asin =2(l /2) the width of central maximum
In experiment of Fraunhofer diffraction from a single slit, f = 0.5m，=5000Å，the width of the slit a=0.1mm. Find the width of central maximum
asin =2(l /2)
the width of central maximum

11. A space craft with a proper length of L0=90m moves at v=0
A space craft with a proper length of L0=90m moves at v=0.8c with respect to one
observer. Measured by the observer, What is the time interval between the craft’s head and end passing through the observer?
△t1 = L/v =2.25×10-7 s