For the same setup of the "Faraday Law" experiment, if the frequency of the magnetic field is changed from 40Hz to 120Hz, how will the emf voltage change? a) will increase three times b) will not change c) will decrease three times d) will change the sign e) will decrease by 80 V f) will increase by 80 V

Emf will become 3 times

So option (a) will be correct answer    

Explanation:

The expression for induced emf is  , here N is number of turns A is  area B is magnetic field and is angular frequency

From the relation we can say that induced emf is directly proportional to frequency

It is given that initially voltage is 80 volt and frequency is increases from 40 Hz to 120 Hz

From the relation we can write

So emf will become 3 times

So option (A) will be correct option

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.

thermal energy is the answer