question_answer

The potentials of the two plates of capacitors are +10 V and -10V. The charge on one of the plates is 40 C. The capacitance of the capacitor is:

A) 2 F                                         

B) 4 F

C) 0.5 F                                      

D) 0.25 F

Correct Answer: A

Solution :

A capacitor is an arrangement which can store sufficient quantity of charge. Suppose, on given a charge q to a conductor, the electric potential of the conductor becomes V. Then, capacitance of capacitor is                 \[C=\frac{q}{V}\] The potential difference across the parallel plate capacitor is \[10V-(-10V)=20V\] \[\therefore \]  Capacitance  \[C=\frac{q}{V}=\frac{40}{20}=2F\] NOTE: The unit farad (F) is very much bigger unit as capacitance of earth, which is a huge body in the universe has a capacitance of \[711\,\,\mu F.\]So, it is not reasonable to discuss such a bigger unit in questions.