1 / 9

Movement of Charges

Movement of Charges. In a Magnetic Field. Revision of the Motor Effect. An electric current interacts with a perpendicular magnetic field . This results in a force. Direction of the force is given by Fleming’s Left Hand Rule. Equation:. 2500 V. Magnetic Field, B , going into the page.

moshe
Download Presentation

Movement of Charges

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Movement of Charges In a Magnetic Field

  2. Revision of the Motor Effect An electric current interacts with a perpendicular magnetic field . This results in a force. Direction of the force is given by Fleming’s Left Hand Rule. Equation: Leeds City College

  3. 2500 V Magnetic Field, B, going into the page 6.3 V a.c. r Electron Gun Charge in a Magnetic Field We find that in a magnetic field, the force acts on a stream of electrons always at 90o to the direction of the movement. Therefore the path is circular. Consider a charge q moving through a magnetic field B at a constant velocity v. The charge forms a current that moves a certain distance, l, in a time t. Leeds City College

  4. Force on the Charge • We know: • Velocity = distance  time • Current = charge  time • F = BIl The t terms cancel out to give: F = B I l = Q I t l = v t Leeds City College

  5. Motion in a magnetic field B field going into the screen The force at 90 o acts as a centripetal force, keeping the electron in a circular path. Force always acts at 90 o Leeds City College

  6. Bear Trap Remember that the direction of the electrons’ movement is in the opposite direction to the conventional current. So if the electrons are going from left to right, the conventional current is going from right to left. When using Fleming’s Left Hand Rule, the current is conventional. Leeds City College

  7. Equation For centripetal force: The v on the left cancels to get rid of the v2 term on the right: For a charge in a magnetic field: Rearranging: We equate these to give: Leeds City College

  8. Uniform B field High frequency a.c. Electromagnet Evacuated chamber Dees Ion source Path of charged particles Cyclotron This is a particle accelerator which relies on a magnetic field to make an electron move out in a spiral. From above: The beam goes out in a spiral, as the particle is getting faster all the time. Leeds City College

  9. Equation If a particle of charge q enters one of the dees with a speed v, it will move in a semi-circular path of radius r. Since f = 1/t For 1 revolution Rearranging gives Therefore: And rearranging gives us: From simple linear motion: And r terms cancel out Which can be equated: Leeds City College

More Related