|
Test
Your EQ #149— Answer
|
Answer
2
When the capacitor was full
of oil, the oil acted as the dielectric and the energy
stored was
| E1 |
= (1/2)CV2 |
|
= (1/2) 10 µF × (10 V)2
= 500 µJ |
After the oil is drained,
the capacitance changes to 1 µF but the charge stays
the same. In order to maintain Q = CV, the new voltage
must be 100V, and the new energy level is
| E2 |
= (1/2) 1 µF × (100 V)2
= 5000 µJ |
We see that there has been
a significant increase in energy. The extra energy was
supplied by whatever force removed the oil from between
the plates (e.g., gravity), which had to pull the oil
away while working against the electric field that was
holding the oil in place.
Contributor: Naveen PN
Published: November-2002
