Which are potential sources of error in the experiment?
variable amounts of metal and magnetic properties of a material
holding the compass at an angle
the color of the bar magnet
unseen magnetic fields (such as from an electrical appliance)
the brand of light bulb used in the circuit
using a dead battery in the circuit

variable amounts of metal and magnetic properties of a material, holding the compass at an angle, unseen magnetic fields (such as from an electrical appliance) and, using a dead battery in the circuit

Explanation: Just did the assignment on ED.

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.