1,000 W = 1 kW
100 W = 0.1 kW
(0.1 kW) x (6 h) = 0.6 kWh <=== energy
(0.6 kWh) x (£0.1359/kWh) = £0.0815 <=== cost of it
Answer:
E=3 x 10^4 N/c
Explanation:
The electric field strength can be found out disk with a uniform positive surface charge density by

σ= charge density
r= radius of the disk
z= position in which we have to find electric field = 15 cm
ε_0= constant ( vacuum permitivity)
putting values we get

solving we get
E=30000 N/c
E=3 x 10^4 N/c