Procedure: I Connect the 3 pairs of leads on the green power supply box to the three inputs on the CRT: The \"6.3V\" leads connect to an (thermionic emission of electrons). The 55V leads (middle knob) connect to V, (deection). The 350V leads ( right knob ) connect to V, (acceleration). Be sure to connect positive lead (red) to the positive side. The large knob controls V, Its value is displayed on the small screen. The small knob controls Vd. Connect a voltmeter to read its value. Set both V, and V, to zero. Ask the teacher to verify your setup BEFORE you turn the power on. I Turn the power on. O O I Part1 I Part2 chn should cause a faint glow inside the small cylinder. Increase V, until the electrons are accelerated a speed large enough to cause a beam to appear. Set V, to the smallest value that produces a clear beam, and record this value. Vary V, and note how it affects the deection Y. Set the CRT facing vertically. Place tape across the screen, perpendicular to the axis ofthe parallel plates. Record the Y=0 position for Vd=0. Vary V, over a range of values that causes the deection to move from one extreme to the other extreme of the front screen. Record '3 or 8 Y vs. V, data points across this range. I *Each time you change Va, adjust the Va knob so that it always read the same constant value you started with: it may drift as V, changes. Set V, to 150V. Set V, to a value that produces the largest measurable deection. Record the value of Y. Change V, to 300V, keeping the same V, value from the previous step. Record the new value of Y. I *Each time you change Va, adjust the Vd knob so that it always read the same constant value you started with: it may drift as Va changes. l. Kinematic analysis: The electrons arrive at the deection plates with a velocity v;r along the x-axis. The width of the plates (along the x-axis) is L. The time it takes to pass this distance is: At. = ( symbols L and vx) (1) During this time interval, the electrons experience a constant acceleration a,- along the y-axis. due to the electric field. Their velocity along the yaxis at the end ofthis interval is: v1. = a}. At] = ( symbols ay, L and vx) (2) It now continues a distance D along the x-axis with no acceleration. The time it takes to travel this distance is: At; = (symbols D and v3) (3) During this time. it will have traveled a distance Y along the y-axis given by: ( multiply equations (2) and (3) together ) Y = vJAl'2 = (symbols a,,. D, vx and L) (4) We now have an expression for Y in terms ofthe acceleration a,. and velocity vx. 2. Relation to electrical Qroperties: Now we relate the kinematic quantities a_,. and v,( to the electrical properties Va and Vd of the CRT. a) 15K depends on V". The kinetic energy ofthe electron, after being accelerated through the potential difference Va, ofthe electron gun is equal to the change in potential energy. Therefore start with the equation K= U5, and solve for v_..2 : 2 _ vx _ (symbols me, qr and Va) (5) b) a). depends on V , . The force on an electron between parallel plates seperated by a distance d and voltage Var is ( hint: F is related to E, and E is related to Vd and d ) F = (symbols q.,vd and d) (6) This means that the acceleration a,- can be expressed as a_,. = Ffmc = (symbols thd and d and rm) (7) . Final res lt Rewrite relation (4) by i: using (7) to get rid of a, and ii: using (5) to get rid of v3 . Final result: Y = (symbols L,D,d, Va and V3) (8) Bonus: (8) is the deection that occurs while the electrons travel the distance D. The electrons are also deflected an additional (but small) amount as they rst travel over the distance L. Show that, if we take this into account, we would get the following expression for Y: \fThe election gun " Sep . 18 "hab # 4 " + - L - TO The Set up ge Fe for deflectid bat for acidaction 1) entens with vat then hashi and vy 2 ) The time for the electron to jet from to bole tzel the electric field . * V . F f_ distance between the plates vottote applied to the plates