iGCSE Physics (0625) 1.7.4 Powers -Exam Style Questions Paper 1- New Syllabus
▶️ Answer/Explanation
Detailed solution:
To find the useful energy transferred, we use the power formula: $P = \frac{\Delta E}{t}$.
First, convert the time from minutes to the SI unit of seconds: $t = 2.0 \times 60 = 120\text{ s}$.
Rearranging the formula to solve for energy gives: $\Delta E = P \times t$.
Substitute the given values: $\Delta E = 60\text{ W} \times 120\text{ s} = 7200\text{ J}$.
This calculation shows that the total useful energy transferred by the boy is $7200\text{ J}$.
Thus, option D is the correct answer.
▶️ Answer/Explanation
Detailed solution:
Power is defined as the rate of energy transfer, measured in watts (W).
One watt is equivalent to one joule per second ($1\text{ W} = 1\text{ J/s}$).
Therefore, a rating of $900\text{ W}$ means the microwave transfers $900\text{ joules}$ of electrical energy into heat and other forms every second.
Options B, C, and D are incorrect as they confuse the units for current, potential difference, and resistance.
▶️ Answer/Explanation
Detailed solution:
Power is defined as the rate of energy transfer, given by the equation $P = \frac{\Delta E}{t}$.
A large power output does not necessarily require a large force or high speed independently; it specifically indicates that a large amount of energy is being transferred or work is being done in a short interval of time.
Therefore, the statement that the engine transfers large amounts of energy each second is the direct and correct interpretation of high power.
Options A and D may be true in certain contexts but are not absolute requirements of power alone, and B is irrelevant.