Question

A spark plug in a bike or a car is used to ignite the air-fuel mixture in the engine. It consists of two electrodes separated by a gap of around 0.6 mm gap as shown in the figure.

To create the spark, an electric field of magnitude 3 x 10⁶Vm^-1 is required,

1. What potential difference must be applied to produce the spark?
2. If the gap is increased, does the potential difference increase, decrease or remains the same?
3. Find the potential difference if the gap is 1 mm.

Answer 1

Separation gap between two electrodes, d = 0.6 mm

d = 0.6 × 10^-3 m

Magnetude of electric field Electric field = E = 3 × 10⁶ V m^-1

Electric field E = `"V"/"d"`

(a) Applied potential difference, V = E . d

= 3 × 10⁶ × 0.6 10^-13 = 1.8 × 10³

V = 1800 V

(b) From equation, V = E . d

If the gap (distance) between the electrodes increased, the potential difference also increases.

(c) Gap between the electrodes, d = 1mm = 1 x 10^-3 m

Potential difference, V = E.d

= 3 × 10⁶ × 1 × 10^-3 = 3 × 103

V = 3000 V