Question

2. A spark plug in a car has electrodes separated by a gap of 0.025 in. To create a spark and ignite the fuel-air mixture in the engine, an electric field of 3.0 x 106 N/C is required in the gap. (a) What potential difference must be applied to the spark plug to initiate a spark? (b) If the separation between electrodes is increased, does the required potential difference increase, decrease, or stay the same? Explain. Answer: a) 1.9 kV b) Use physics reasoning here!

Answer 1

(a) The potential difference applied across the plug is, delta V = Ed delta V = (3 times 10^6 N/C) (0.025 in) delta V = (3 times 10^6 N/C) (0.000635 m) delta V = 1.905 times 10^3 V delta V = 1.9 kV (b) The potential difference increases with increasing the separation. Since the potential difference is directly proportional to the separation.