Power Flashcards

All 6 cards in this deck

How is power defined?

The rate at which energy is transferred (or the rate at which work is done).

One watt is equal to how many joules per second?

$1\text{ W} = 1\text{ J/s}$

What is the equation for power in terms of work done?

power (W) = work done (J) ÷ time taken (s)

What are the steps to find the time taken for a device to transfer a given amount of energy?

e.g. a 50 W lamp transferring 400 J

1. Write the equation: power = energy transferred ÷ time
2. Rearrange: time = $400 \div 50$
3. Time = 8 s

What are the steps to calculate a person's power output when climbing stairs?

e.g. a 60 kg person climbs 4 m in 10 s, $g = 10$ N/kg

1. Work done = $mg\Delta h = 60 \times 10 \times 4 = 2400$ J
2. Power = work done ÷ time = $2400 \div 10$
3. Power = 240 W

True or false? If two machines transfer the same amount of energy, the one that takes less time has the greater power.

True. Power is the energy transferred each second.