THERMAL EFFECTS AND FIELDS

**Take G = 6.67x10**

^{-11}Nm^{2}kg^{-2}Permittivity of free space (Ɛ_{o})= 8.84x10^{-12}Fm^{-1 }Electron charge = -1.6x10^{-19}C Electron mass = 9.1x10^{-31}kg**1. What is an adiabatic change?**

**2. What is the definition of gravitational potential energy?**

**3. What is meant by escape velocity?**

**4. Define specific heat capacity.**

**5. Define electrical potential.**

**6. Define an isothermal change.**

**7. What is meant by the greenhouse effect?**

**8. What determines whether a planet can retain its atmosphere?**

**9. Give two similarities between electrostatic force and gravitational force.**

**10. Write down the first law of thermodynamics, explaining all the symbols that you use.**

**11. In thermal conductivity if a metal pipe is lagged with an equal thickness of insulator:**

**(a) Across which will there be the greatest temperature difference or are they equal**

**(b) Through which will there be the greatest heat flow or are they equal?**

**12. Give two differences between electrostatic force and gravitational force.**

**13. What is the electric field inside a hollow charge conductor?**

**14. How does the electrical potential vary between two parallel charged plates?**

**15. How does the electric field vary between two parallel charges plates?**

**16. In gas equations do you use Kelvin or Centigrade?**

**17. Write down two assumptions made when deriving the kinetic theory of gases equation.**

**18. Under what conditions is Boyle’s law obeyed most closely for a real gas?**

**19. What is the change in internal energy for an ideal gas undergoing an isothermal change?**

**20. What is another way of writing the gravitational potential gradient in a field?**

**21. What are the units for electrical potential?**

**22. Write down two alternative units for the electric field intensity.**

**23. Write down an equation relating the root mean square velocity of gas molecules to the gas density defining any terms that you use.**

**24. What happens to a beam of light near a neutron star and why?**

**25. What is a black hole?**

**26. Write down an expression for Boltzmann’s constant.**

**27. What is the energy of a gas molecule of mass m at temperature T?**

**28. Give three properties of a synchronous of geostationary satellite.**

**29. Between which points on two planets must their separation be measured when calculating the gravitational attraction between them?**

**30. Define specific latent heat.**

**31. What happens to the temperature of a material while it is changing its state?**

**33. Which type of surface is the best emitter of thermal radiation?**

**34. What is the heat input for an ideal gas undergoing an adiabatic change?**

**35. Define absolute zero.**

**36. Define the triple point of water.**

**37. Define the unit of temperature (K).**

**38. Write down an equation for the energy changes for an electron being accelerated in a uniform electric field.**

**39. What is the relation between the electric field intensity at a point in a field and the force on a charge Q placed at that point?**

**40. What is the formula for the electric field intensity at a distance R from a point charge Q in a vacuum?**

**41. What is the formula for the electrical force on a charge q at a distance R from a point charge Q in a vacuum?**

**42. Write down two uses of static electricity.**

**43. A gas of volume 5m**

^{3 }at a temperature of 18^{o}C is heated to 100^{o}C, the pressure rising from 1.0x10^{5 }Pa to 2.4x10^{5}Pa. What is the new volume of the gas?**44. An electric field exists between two parallel plates 10cm apart and with a potential difference of 400V between them. Calculate the electric field intensity at a point 5 cm from the positive plate**

**45. Calculate the value of the gravitational intensity at the surface of a planet of mass 5x10**

^{25}kg and radius 3x10^{5 }m.**46. What is **

_{o}?**47. How much energy is needed to vaporise 3.5 kg of water at 100**

^{o}C? The specific latent heat of vaporisation of water is 2.25x10^{6}Jkg^{-1}.**48. A gas is expanded isothermally, expanded adiabatically, compressed isothermally and finally compressed adiabatically. What is the area of the closed loop on the PV diagram equal to?**

**49. A vacuum flask contains liquid nitrogen. The outer surface of the inner walls of the flask is silvered – why?**

**50. How can you get an indication of the electric field intensity from a diagram showing the field lines?**

**51. Calculate the increase in velocity of an electron that has been accelerated through a potential difference of 2.5 kV.**

**52. Define electrical potential energy.**

**53. Define electric field intensity.**

**54. Which emits radiation of longer wavelength – a black body at 300**

^{o}C or a black body at 500 K?**55. If the Earth takes 365 days to orbit the sun at a distance of 150x10**

^{9}m calculate the mass of the Sun.**56. In an adiabatic expansion does the temperature of a gas rise or fall?**

**57. In an isothermal compression does heat energy enter or leave the system?**

**58. Write down the equation that you would use to find the charge (Q) on an oil drop of mass m suspended in an electric field of intensity E.**

**59. Such a drop is held between two horizontal plates 20 mm apart with a p.d of 250V between them. The drop has a mass of 0.2 mg. Calculate the charge on the drop.**

**60. A gas is compressed isothermally, expanded adiabatically, expanded isothermally, and finally compressed adiabatically. What is the area of the closed loop on the PV diagram equal to?**

**61. What is the root mean square velocity of the molecules in a gas of density 1.04 kgm**

^{-3 }at a pressure of**10**

^{5}Pa?**62. Why do breezes blow from the sea to the land in the evening after a hot day?**

**63. What are the units for thermal conductivity?**