Fig. 1 shows a solar garden light installed beside a footpath. In daylight, a solar cell transfers energy from radiation to electrical energy and charges a ...
Question 1 Report
Fig. 1 shows a solar garden light installed beside a footpath. In daylight, a solar cell transfers energy from radiation to electrical energy and charges a rechargeable battery. At night, a light sensor closes the circuit to an LED. The battery has a potential difference of 3.6 V. When the LED is operating, the current is 0.080 A. A resident wants the light to operate for as long as possible after a cloudy day.
(a) Which energy store increases when the battery is charged? [1]
(b) Describe the useful energy transfer made by the solar cell. [2]
(c) Calculate the power transferred to the LED. [2]
(d) Calculate the charge supplied by the battery in 3.0 hours. [3]
(e) Give two ways the resident could increase the operating time of the light. [2]
Answer Details
(a) Charging the battery increases its chemical energy store. [1]
(b) The solar cell transfers energy from solar radiation to electrical energy. This electrical energy charges the chemical energy store of the battery. [2]
(c)
\[P=VI=3.6\text{ V}\times0.080\text{ A}=0.288\text{ W}\]
The power transferred to the LED is 0.288 W, or 0.29 W. [2]
(d)
\[3.0\text{ hours}=3.0\times3600=10800\text{ s}\]
\[Q=It=0.080\text{ A}\times10800\text{ s}=864\text{ C}\]
The battery supplies 864 C of charge in 3.0 hours. [3]
(e) Two valid ways are to use a larger battery and use a lower-current LED. A more efficient LED or positioning the solar cell where it receives more radiation would also increase operating time. [2]
Download The App On Google Playstore
Everything you need to excel in your exams
