A solar cooker is used at a campsite, as shown in Fig. 1. Curved reflective panels direct radiation towards a black metal cooking pot. Water in the pot incr...
Question 1 Report
A solar cooker is used at a campsite, as shown in Fig. 1. Curved reflective panels direct radiation towards a black metal cooking pot. Water in the pot increases in temperature from 20 degrees C to 70 degrees C. The cooker is placed in still air to reduce cooling. The black surface absorbs radiation well, but not all energy from the Sun heats the water. Some energy is reflected, and some warms the metal and the air around the pot.
(a) Which type of energy transfer heats the pot from the Sun? [1]
(b) What colour surface is best for absorbing this radiation? [1]
(c) Describe one way the cooker reduces energy transfer to the air. [2]
(d) When would the cooker transfer energy to the water at the greatest rate? [1]
Answer Details
- The Sun heats the pot by radiation, specifically infrared radiation. [1]
- A black, preferably dull black, surface absorbs radiation best. [1]
- Keeping the cooker in still air reduces convection: there is less movement of warmed air away from the pot, so less energy is transferred to the surroundings. A lid reducing convection or insulation reducing conduction would also be valid. [2]
- The energy transfer rate is greatest in bright sunlight, when radiation intensity is greatest. [1]
Download The App On Google Playstore
Everything you need to excel in your exams
