In an AC circuit, magnetic reversal due to phase difference between current and voltage occurs 50 or 60 times per second. A capacitor helps to improve the power factor by relieving the supply line of the reactive power.

Answer: B) Eleven Explanation: List of fundamental duties of the citizens of India in Article 51A of the Indian Constitution : 1. to abide by the constitution and respect its ideal and institutions; 2. to cherish and follow the noble ideals which inspired our national struggle for freedom; 3. to uphold and protect the sovereignty, unity and integrity of India; 4. to defend the country and render national service when called upon to do so; 5. to promote harmony and the spirit of common brotherhood amongst all the people of India   transcending religious, linguistic and regional diversities, to renounce practices derogatory to the   dignity of women; 6. to value and preserve the rich heritage of our composite culture; 7. to protect and improve the natural environment including forests, lakes, rivers, and wild-life       and to have compassion for living creatures; 8. to develop the scientific temper, humanism and the spirit of inquiry and reform; 9. to safeguard public property and to abjure violence; 10. to strive towards excellence in all spheres of individual and collective activity 11. who is a parent or guardian , to provide opportunities for education to his child, or as the case may be, ward between the age of six and fourteen years.

Answer: B) Strontium Explanation: We know that, Elements in the same group of the periodic table have similar characteristics. Here Magnesium and Strontium shared some similar properties because they both belong to the same group. Sr is the chemical symbol for strontium which is a group two element; it has atomic number of 38.