This preview shows pages 1–5. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: 5004. Mm gozx Sim Paka/é to?“ Wow cm at Ag/qu( farce/Dy”
accc/emé‘pﬁ {:4 #LL dink/7'00; 0! E v—9 ‘2} [as o [‘1 63:0‘ ﬂow jémeQ/(y/
Celt Lmqﬂhaﬂc fie/of o/orj M0 Lam/4) Q5 _L (mislead ‘> y 0 B a] PQHLI'CIL LL QCLt/CVCZ‘QOI flf’raaﬁll!
S R E) “r *9 CVOSSLS PM»: a! x,y: 0,8
T 7X? 5) (park'cft my mm 00, a JamiCivrclc.
x',y: 0,0 Ehcl" 535’ '3 E‘S/ mamtnvlbm “CW/0" F: 277.2’E‘5‘M C) m (we), :7 27% 2 WW’
7/47 .13 3:) (Oo‘rdl‘vm/E {0v (yaua'vj her/aha 1‘5 (ZRIS) Massachusetts Institute of Technology Spring Term 2005 8.02X Electricity and Magnetism Experiment Electric Breakdown (EB) Problems
(20 points total) Lab Hours: Mondays: 35 pm, Tuesday: 7:309:30 pm, Wednesday: 7:309:30 pm,
Thursday: 35 pm, Fridays: 123 pm Due Date: Checkoff by April 4 in lab 4355. To satisfy the checkoff for experiment
EB, you must do the following tasks. You will be graded according to the following criteria: 1. Your EB experiment works properly. 2. The EB experiment is setup according to diagrams that are shown in the lab
writeup. 3. You should be prepared to brieﬂy explain the questions below. Bonus Points Policy: Checkoffs that are ﬁnished on Mon Mar 28 will receive 2
extra points, and checkoil's on Tue Mar 29 will receive 1 extra point. Experiment EB (Electrical Breakdown) Connect M 1 on the IOOODCV range (use COM and +DC1000V for the test
iead inputs) across the HVPS output. We will call this voltage V5. Connect MMM 2 on
the SOODCV range (use COM and +VQA for the test lead inputs and the same switch
setting as for the IOOODCV range) across one of the IMQ resistors. We will call this voltage K. Figure 1: Multimeter connections for Experiment EB Start with the tungsten rod touching (shorted). Turn the wingnut on the Clothespin
smoothly to the 0.025 position, one fourth of the way to the 0.1mm setting. Raise the HVPS voltage slowly until the second meter just begins to deﬂect, indicating breakdown
with the formation of an arc. Record the voltage V0 with M 1 across the HVPS and the voltage V1 with MMM 2 across the IMQ resistor at which this happens. Repeat for the three remaining gap widths, and repeat the entire procedure three times. Enter your
data in the tables below. Analysis Plot the average breakdown voltage vs. gap, and determine either a best single
value of the breakdown electric ﬁeld or a range of values. Express your results in V/rnm. Data Table: Breakdown Voltages for Various Spark Gap Separations Gap Separation Breakdown Breakdown Breakdown Breakdown
VoltageK} [V] VoltageVo [V] VoltageV; [V] Voltage% [V] L50 Problem 1: Experiment EB a) What is the number of particles per m3, (the number density n), for an ideal gas at
standard temperature and pressure? b) Deﬁne the mean free path for an electron in a gas to be the average distance A an
electron travels before it collides with an air molecule. If an electron travels close enough
to an air molecule it will collide. The impact parameter b, is deﬁned to be the radius of a circular cross sectional area of effective area .7rb2 that the air molecule presents as a target
to the electron. This means that there must be at least one air molecule in the volume itan that the electron could collide with. Find an expression for the number density n of
air molecules, in terms of the mean free path A, and the impact parameter b. c) When the electron is placed in a gap of width d and gap voltage AVW, how much kinetic energy per charge does the electron acquire if it travels a distance equal to the
mean free path A? d) The energy per charge necessary to ionize air molecules, the ionization voltage, is
AV. ~10 V. If the electron gains a kinetic energy per charge equal to the ionization f0" voltage then the electron will ionize the air molecule. Using your result from part c),
derive an expression for the mean free path it in terms of the gap width (1, gap voltage Alf“), andionization voltage AK”. e) Use your experimental results where you found the breakdown electric ﬁeld (average
gap voltage / gap width) necessary to ionize air molecules. Use that result to calculate
the mean free path A. 0) ﬂuasqoivo’; /i/mmLCv 3
)mot —. 22.91 = 0~OZLLIW aongh 1— . _3
1:17 DéhSt'tlx/ ﬁt W __ W b) kip3 H ("y/main of Doll/twat: 2'74} mud (maze/y, 0p] acct/stile [maﬁa/c. ,1 “mi, cw] Ma: 6. O 211023 Wo/CCm/es/Ma( —l—"‘ [ dimengom 0‘1 V‘ : lift}
,3 ({CCJVC'M C, (It‘d/ﬁé 8) C) K: AM rd}.€~ Adi/Sara ’ chrt 6 til/1w
0” k” Alloy 2) A: $3; w.
Al/W /"' R ...
View
Full
Document
 Spring '07
 Hudson

Click to edit the document details