Physics

posted by .

What is electric field required at the tip of sharp needle to ionize air?

  • Physics -

    See here for details:

    http://en.wikipedia.org/wiki/Paschen's_law

    You can use that the mean free path for electrons in air is about 5*10^(-7) meters. You always have ions and electrons in the air, so what needs to happen is that an electron has to be accelerated due to the applied electric field so that it has enough energy to ionize an atom. This means that the potential difference over 5*10^(-7) needs to be a few volts (ionazation energy is typicxally of the order of a few eV), so the electric field needs to be of the order of 10^7 Volt/meter.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. long physics E&M

    A Geiger counter detects radiation such as alpha particles by using the fact that the radiation ionizes the air along its path. A thin wire lies on the axis of a hollow metal cylinder and is insulated from it. View Figure A large potential …
  2. Physics E&M

    A Geiger counter detects radiation such as alpha particles by using the fact that the radiation ionizes the air along its path. A thin wire lies on the axis of a hollow metal cylinder and is insulated from it. View Figure A large potential …
  3. Physics

    An electron moving to the right at 3.0% the speed of light enters a uniform electric field parallel to its direction of motion. If the electron is to be brought to rest in the space of 4.5 cm, determine the following. What direction …
  4. physics

    3. What is the magnitude of the electric field strength E such that an electron, when placed in the field, would experience an electrical force equal to its weight?
  5. calculus

    the needle of the scale is 27 cm long. find the distance the tip of the needle travels when rotates 74 degree
  6. Physics

    After rubbing a balloon against someone's hair, a balloon has accumulated a static electric charge. The air inside the balloon has the same density as the air outside of the balloon, and the balloon itself weighs 1.41mN. How many free …
  7. Physics

    A point charge Q1=-2 microcoulomb is located at x=0, and a point charge Q2=+8 microcoulomb, is placed at x=-0.5 on the x axis of a cartesian coordinate system.The goal of this problem is to determine the electric field,at various points …
  8. physics

    Which of the following statements about electric field lines due to static charges are true?
  9. physics

    A magnetic needle is disposed inside a horizontal coil. In the abscence of any electric current the needle is observed to get oriented in a direction perpendicular to the x'x of the coil. a) what is the direction of the terrestrial …
  10. physics

    A 0.035 kg spherical oil droplet has charge of +1×10-7C. A uniform electric field is acting upwards as shown below. What strength of electric field is required to make the sphere float in the air without moving?

More Similar Questions