Physics - Power
OCR A-Level Physics 2022
Power and efficiency
If velocity is the rate of change of displacement, work done is?
The rate of change of energy.
How is efficiency calculated?
\[\frac{\text{useful output energy}}{\text{total input energy}} \times 100\%\]
Electrical power
If
\[P = \frac{W}{t}\]
and
\[W = VQ\]
How could you write the formula for $P$?
\[P = \frac{VQ}{t}\]
If
\[V = IR\]
and
\[P = IV\]
How could you rewrite the power equation?
\[P = I^2R\]
If
\[I = \frac{V}{R}\]
How could you rewrite the power equation?
\[P = \frac{V^2}{R}\]
Given a power, $P$, how can you calculate the work done $W$ over a given time $t$?
\[W = Pt\]