Work
where $$ \theta = $$ angle of force to direction of movement
No work : displacement = 0, force = 0, force $$ \perp $$ displacement
SI: 1 joule = 1 n$$ \cdot $$m = $$ 1 kg \cdot m^2/s^2 $$
Energy (measured in joule/sec)
Ability to perform work
Neither created nor destroyed, only transformed
kinetic ~ = energy in motion
potential ~ = energy stored by object.
Measured by amount of work done.
Power
Rate of doing work $$ P = W/t $$ where $$W = Fd $$
Unit: Power doesn’t have direction $$ \Rightarrow $$ scalar
Watt = joules/sec (j/s) = $$ 1 kg \cdot m^2/s^2 = .24 c/s $$ (calories/sec)
= Power need to do 1 joule of work in 1 second
P = VI $$ or $$ P = VA = V^2/R
Electrical Energy
Unit: joule = watt$$\cdot$$sec (w{\cdot}s)
= 1 amp. of current flows through the circuit for 1 sec. when the potential different of 1 volt is applied across it.
1 kwh = 36 x 10^5 w{\cdot}s$$ or joules.