Which of the following would cause an iron bar to start generating a magnetic field? A Orienting the iron bar so that it points to the North pole. B Labeling the ends of the bar with "N" and "S".
C Melting the bar completely and letting it cool down slowly.
B Wrapping the bar with a coil of wire that has an electric current.

Wrapping the bar with a coil of wire that has an electric current.

Explanation:

To cause an iron bar to start generating a magnetic field, wrap the bar with a coil that has an electric current.

Wrapping the bar with a coil of wire that has electric current can cause an iron bar to start producing magnetic fields. This way, the iron bar becomes a magnet.

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.

im sorry i dont know