Ether slipped 15% to a price of $1,497 while XRP sank 21% to trade around 45 cents.On Monday, Yellen called bitcoin an “exceptionally ineffective method of carrying out deals” and alerted about its use in illegal activity. Bitcoins network consumes more electrical power than Pakistan, according to an online tool from scientists at Cambridge University.Yellen likewise cautioned about the threats of bitcoin investing to retail investors Monday. Bullish financiers claim the cryptocurrency can act as a hedge against rising inflation.But skeptics alert that bitcoin is and has no intrinsic worth one of the biggest market bubbles in history.