What is a resistor? Resistors are passive electrical components that limit electric current. Resistor is a passive electrical component. Its primary function is to limit the flow of electric current. To understand the function and working of resistors, let us consider an uniform hollow pipe with water flowing through it. If the two similar pipes are now joined with a narrow pipe relatedly having less diameter or cross-sectional area. Then the water current will be resisted by the pipe having less cross-sectional area. It means this particular section of pipe will act as a resistor for water current. Similarly, a resistor by limiting or reducing the flow of charge carrier, reduces the flow of electric current in a circuit. What is OHM’S Law? Voltage across a resistor is directly proportional to the current passing through it. V ยต I or, V=R.I Where, R is a proportionality constant, it is called resistance of a resistor. It means that if the current