4. Um chuveiro elétrico instalado em uma rede de
220 V, quando em funcionamento, é percorrido
por uma corrente elétrica de intensidade 20 A.
Determine a energia elétrica consumida, em
quilowatt-hora, durante um banho com duração
de 15 min.

Explanation:

The question is:

1. Data:

a) V = 220V

b) I = 20 A

c) E = ?

2. Physical principles and formulae

Power, P, is equal to the product of the potential difference, V, by the current, I:

The energy, E, is equal to the product of the power, P, and the time, t:

3. Solution

answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.