oldhw 20 - nguyen (jmn727) oldhomework 20 Turner (59070)...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
nguyen (jmn727) – oldhomework 20 – Turner – (59070) 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 (part 1 oF 3) 10.0 points A device (“source”) emits a bunch oF charged ions (particles) with a range oF ve- locities (see fgure). Some oF these ions pass through the leFt slit and enter “Region I” in which there is a vertical uniForm electric feld (in the ˆ direction) and a 0 . 3 T uniForm mag- netic feld (aligned with the ± ˆ k -direction) as shown in the fgure by the shaded area. q m Region oF Magnetic ±ield 0 . 3 T +2400 V 0 . 6 cm x y z 36 cm Region I Region II Figure: ˆ ı is in the direction + x (to the right), ˆ is in the direction + y (up the page), and ˆ k is in the direction + z (out oF the page). In which direction (relative to the coor- dinate system shown above) should the mag- netic feld point in order For positively charged ions to move along the path shown by the dot- ted line in the diagram above? 1. v B b v B b = + ˆ k correct 2. b v B b = 0 ; direction undetermined 3. v B b v B b = ˆ k Explanation: To obtain a straight orbit, the upward and downward Forces need to cancel. The Force on a charged particle is v F = v F E + v F B = q ( v E + vV × v B ) . ±or the Force to be zero, we need v F E + v F B = 0 , or v F E = v F B . ThereFore, the Forces are equal and opposite and the magnitude oF Forces are equal; i.e. , b v F E b = b v F B b . The Force due to the magnetic feld provides the centripetal Force that causes the negative ions to move in the semicircle. As the positively charged ion exits the re- gion oF the electric feld, v F B = q vV × v B , so by the right-hand rule the magnetic feld must point out oF the page p or in the + z -direction + ˆ k P , since the Force v F is in the direction up the page; i.e. , “+ˆ q | q | = + vV b vV b = +ˆ ı v B b v B b = ?
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/21/2010 for the course PHY 303L taught by Professor Turner during the Spring '08 term at University of Texas at Austin.

Page1 / 4

oldhw 20 - nguyen (jmn727) oldhomework 20 Turner (59070)...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online