Question

When the potential difference between the student and a nearby earthed metal dome reaches 15kV, a spark jumps between the student and the earthed dome. The spark transforms 30mJ of energy into heat, light and sound. Calculate the charge carried by the spark. Give the correct unit and state any equations you use.

Answer 1

Answer: 2×10⁻⁶ Q

Explanation:

15kV = 15000 V

30mJ = 30/1000 J = 0.03 J

Potential difference is the energy carried per charge. Therefore

V = E/Q

⇒ Q = E/V

⇒ Q = 0.03 J / 15000 V = 0.000002 = 2×10⁻⁶ Q

Hope it helped