iGCSE Physics (0625) 1.7.3 Energy resources Paper 4 -Exam Style Questions- New Syllabus

(a)
For the correct answer:
Black is a good absorber of radiation, leading to more electricity generation.

Dark, dull surfaces are significantly better absorbers of infrared radiation compared to light or shiny surfaces. By using black panels, the system absorbs a higher percentage of the incident solar energy and reflects less away.

(b)
For the correct calculated value:
22 kW (or 22000 W)

Efficiency is defined as Efficiency= Total Power Input Useful Power Output ​ . Rearranging for total input gives Input= Efficiency Output ​ . Substituting the values: Input= 0.16 3.5 kW ​ =21.875 kW, which rounds to 22 kW.

(c)
For the correct answer:
Alternating current reverses direction, while direct current flows in only one direction.

Direct current (d.c.) is characterized by a constant direction of charge flow. In contrast, alternating current (a.c.) periodically reverses its direction and changes its magnitude continuously with time.

(d)
For the correct answer:
Electricity can be used when there is no Sun (e.g., at night or during cloudy weather).

A rechargeable battery acts as an energy store, allowing the excess electricity produced during peak sunlight to be saved for later use, ensuring a reliable power supply during the night.

(e)
For the correct calculated value:
29000 C

Using Q=I×t, convert time to seconds: 2.0 hours=7200 s. Thus, Q=4.0 A×7200 s=28800 C. Rounding to two significant figures gives 29000 C.