The diagram shows a rescue volunteer charging a radio from a portable solar panel. In bright sun, the panel provides a potential difference of 8.0 V and a c...
Question 1 Report
The diagram shows a rescue volunteer charging a radio from a portable solar panel. In bright sun, the panel provides a potential difference of 8.0 V and a current of 0.75 A to the charger. The radio battery gains 2700 J of energy in 10 minutes. Some energy is transferred to thermal energy in the charger and cable. The volunteer wants to compare the electrical energy supplied with the useful energy stored in the battery.
(a) What is the electrical power supplied by the solar panel? [2]
(b) Give the electrical energy supplied in 10 minutes. [2]
(c) Explain why the energy supplied is greater than the energy stored. [2]
Answer Details
(a) Use \(P=VI\): \[P=8.0\text{ V}\times0.75\text{ A}=6.0\text{ W}\] [2]
(b) \[10\text{ min}=10\times60=600\text{ s}\] \[E=Pt=6.0\text{ W}\times600\text{ s}=3600\text{ J}\] [2]
(c) The supplied energy is greater because some energy is dissipated in the charger and cable, mainly as thermal energy due to resistance. Thus not all supplied electrical energy is stored in the battery. [2]
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