Question: The RC time constant, also called tau, the time constant (in seconds) of an RC circuit, a irst order RC circuit is composed of one resistor and one capacitor and is the simplest type of RC circuit, and is equal to the product of the circuit resistance (in ohms) and what (in farads)? 
Sentence (from "RC circuit"): A first order RC circuit is composed of one resistor and one capacitor and is the simplest type of RC circuit.
Relevant evidence: No