Calculate the work done in a resistor of 20 ohm carrying 5A of current in 3 hours.

Options

A. 1.5J
B. 15J
C. 1.5kWh
D. 15kWh

Answer

A

Explanation

From conservation of energy,
Potential energy = translational kinetic energy + rotational kinetic energy
`therefore mgh=(1)/(2)mv^(2)+(1)/(2)Iomega^(2)`
Where moment of inertia of sphere
`I=(2)/(5)MR^(2)andomega=(v)/(R)`
`therefore mgh=(1)/(2)mv^(2)+(1)/(2).(2)/(5)MR^(2).(v^(2))/(R^(2))`
`therefore mgh=(7)/(10)mv^(2)`
`therefore v=sqrt((10)/(7)gh)`
Hence, if `vgesqrt((10)/(7)gh)`, then sphere can climb the incline.