Assuming that the speed of the electrons is zero as they are emitted from the filament and that as they reach the anode it is v, find an expression relating the final speed v to the charge on an electron, the mass of an electron and deltaV, and hence calculate the speed v of the electrons after passing through a voltage difference of 120 kV.(adsbygoogle = window.adsbygoogle || []).push({});

I'm new to this, but the equation I have come up with is

v = √ 2QΔV

m

I then get this:

√ 2 x (1.602 x 10-19J) x (120-0 x 103eV) = √ 3.8448 x 10-14

8.2 x 10-14 J 8.2 x 10-14 J

√0.46887804 = 0.6847466977

To two significant figures and in scientific notation this is 6.8 x 10-1 eV s-1

I think I'm tying myself in knots - please help!

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# Homework Help: Relating final speed of electron to its charge mass and voltage difference

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