iGCSE Physics (0625) 1.7.4 Power -Exam Style Questions Paper 2 - New Syllabus
▶️ Answer/Explanation
Detailed solution:
The energy transferred by the heater is given by $\Delta E = P \times t$, where $P$ is power and $t$ is time.
Specific heat capacity $c$ is defined by the thermal energy equation $\Delta E = mc\Delta \theta$.
By substituting the expression for energy, we get $Pt = mc\Delta \theta$.
Rearranging this formula to make $c$ the subject gives $c = \frac{Pt}{m\Delta \theta}$.
This matches the expression provided in Option B.
▶️ Answer/Explanation
Detailed solution:
Power is defined as the rate of energy transfer, meaning 1 watt equals 1 joule per second.
A rating of 900 watts therefore means the appliance transfers 900 joules of electrical energy into other forms (like heat) every second.
Options B, C, and D incorrectly associate power with units of current (amperes), potential difference (volts), or resistance (ohms).
This matches the syllabus definition of power in topic 1.7.4.
▶️ Answer/Explanation
Detailed solution:
Power is defined as the rate of doing work or the rate of energy transfer, given by $P = \frac{\Delta E}{t}$.
A large power output does not strictly require a large force, a fast speed, or a large engine volume.
It specifically means that a significant amount of energy is being transferred or converted per unit time.
Therefore, a vehicle engine with large power must transfer large amounts of energy each second.
This makes Option C the only necessarily correct statement based on the definition of power.