What can cause a change in the direction of a magnetic field?

Change in the direction of current in a wire will change the magnetic field caused by that wire

Explanation:

As we know by Biot Savart law that magnetic field due to a current carrying element is given by

so here if the direction of current in the wire reversed then it will change the direction of length vector

This will reverse the direction of magnetic field at a given space

So magnetic field produced by a current carrying element only depends on the direction of the current so on reversing the direction of current we can change the magnetic field direction

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.