In air you need an electric field of strength 3x106 V/m to rip some electrons of

Question

In air you need an electric field of strength 3x106 V/m to rip some electrons off the air and make a spark. The spark plugs in your car have a gap between their electrodes of around 0.025 inches. (a) What's the voltage difference you need to apply to the two electrodes in order to get the spark plug to actually spark? (b) what happens to the needed potential when you increase the separation between electrodes and why? (c) find the voltage needed to spark if the gap increases to 0.050 inches. (d) Why might re-gapping your plugs help a rough-running engine?

Explanation / Answer

E=3x106 V/m , 1 inch =0.0254 m

(a) d =0.025 inches =0.000635 m

V =Ed =3x106 x 0.000635 =1905 V

(b) increased

(c) d =0.05 inches = 0.00127 m

V=Ed=3x106 x 0.00127 =3810 V

(d) U =qV

Due to re gapping of plugs, electric potential energy increases as well as electric potential energy is increased, so engine run freely.

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