6.06 Example questions involving power and energy.

Example 1.
Calculate the total power consumed in the circuit below and the energy dissipated in 1 minute.

example 1

R_T = R₁ + R₂ .
R_T = 25 W .
I = E/R_T .
I = 0.2 A .
P = VI .
P = 1W .
W = Pt ( t = 1min = 60s) .
W = 60J .

Example 2.
Calculate the power dissipated by R2 and the energy dissipated by R₂in 20 seconds.

example 2

R_T = R₁ + (R₂ x R₃)/(R₂ + R₃) .
R_T = 5W .
I = E/R .
I = 1.6A .
using the current divider rule, I₂ = I_T x R₃/(R₂ + R₃) .
I₂ = 0.96A .
P₂ = I²R₂ .
P₂ = 3.686 W .
W = P₂t .
W = 73.72 J .