Q.

A point charge causes an electric flux of –2×104 Nm2C–1 to pass through a spherical Gaussian surface of 8.0 cm radius, centred on the charge. The value of the point charge is: (Given ε0=8.85×10–12C2N–1m–2)          [2025]

1 –17.7×10–8 C  
2 –15.7×10–8 C  
3 17.7×10–8 C  
4 15.7×10–8 C  

Ans.

(1)

ϕ=–2×104Nm2C

ϕ=qε0

⇒ q=ε0ϕ=(8.85×10–12)×(–2×104)

q=–17.7×10–8C