This Sunday (20), the first phase of the entrance exam Unicamp (Campinas State University).
The evidence, provided by 58,4 thousand people, counted on questions about solar energy in the notebook of Physics, highlighting the role played by the sector in energy solutions and sustainable development.
Considered one of the best universities in Latin America, Unicamp 69 undergraduate courses, more than 200 postgraduate programs, 83 of which are stricto sensu and 120 lato sensu, and has more than 39 thousand students enrolled.
Check out the questions:
1st Question
The question describes a system consisting of a solar panel that generates electrical energy with a power of 462 W and a potential difference of 42 W. In addition to a charge controller and a battery.
The goal is to store this energy in a battery that has a potential difference of 12 V. The charge controller adjusts this potential difference between the solar panel and the battery.
So, what are the values of the electrical currents of the panel and the battery?
To resolve the issue, it is necessary to make calculations based on the relationship between the power and voltage at the solar panel terminals.
P = Electrical power.
U = Electrical voltage/potential difference in V (volt).
i = Electric current in A (ampere)).
Calculation for the panel:
Calculation for the battery:
Resposta:
Alternative A
The current at the solar panel terminals i panel is 11 A.
The current at the terminals of the i bat battery is 38,5 A.
The charge controller allows this adjustment between the current and voltage of the solar panel and the battery, ensuring that the energy generated is stored efficiently, despite the voltage differences between the panel and the battery.
2st Question
The question asks the candidate to calculate the efficiency of a solar panel. To do this, it is necessary to calculate the ratio between the electrical energy generated by the panel and the solar energy that falls on it.
Calculation:
Alternative B
Converting 0,2 to a percentage, the solar panel efficiency is approximately 20 %.
In other words, 20% of the solar energy that hits the panel is converted into electrical energy, while the rest is lost, mainly in the form of heat.
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