Westinghouse and Edison fought what was known as the war of the currents. Eventually, Westinghouse triumped using Alternating Current for power distribution. Alternating current is better for power generation because

First of all, we start with some definitions:

- Direct Current (DC) is a current in which the direction of the current does not change with time

- Alternating Current (AC) is a current in which the direction of the current keeps changing periodically

Alternating Currents are used instead of Direct Currents to send electricity to houses. The reason behind this is mainly a higher efficiency.

In fact, it is possible to demonstrate that the power loss along transmission lines is smaller when the electricity is sent at higher voltages (order of kilovolts or megavolts). Therefore, electricity is sent at higher voltages; however, it must return to lower voltages in order to be safely used in houses.

In order to reduce the voltage before electricity is used in the houses, transformers can be used (transformers are device that are able to increase or reduce the voltage in an AC current). However, transformers only work with Alternating Currents, while changing voltages for a direct current is much more difficult and require more expensive devices.

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.