# Why do we use resistor?

Resistance is the measure of opposition to electric current. A short circuit is an electric circuit offering little or no resistance to the flow of electrons. Short circuits are dangerous with high voltage power sources because the high currents encountered can cause large amounts of heat energy to be released.
A.

### What is a resistor and what does it do?

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.
• #### What does a resistor do in physics?

In short: Resistors limit the flow of electrons, reducing current. Voltage comes about by the potential energy difference across the resistor. The mathematical answer is that a resistor is a two-terminal electric device which obeys, or you could say enforces, Ohm's law: V=IR.
• #### What is the use of a variable resistor?

Simply put, a variable resistor is able to have its electrical resistance adjusted. These devices are used when working with electrical circuitry because they help to control voltage and/or currents. They specifically work with voltage and currents that are a part of the circuit.
• #### What is a variable resistor and how does it work?

A variable resistor is very important. It allows you to build a circuit with some degree of control. For example, a volume knob can be a variable resistor. It can act as a control on the amount of current flowing.
B.

### How does a resistor work?

Devices called resistors let us introduce precisely controlled amounts of resistance into electrical circuits. Photo: Four typical resistors sitting side by side in an electronic circuit. A resistor works by converting electrical energy into heat, which is dissipated into the air.
• #### Do resistors have a polarity?

If I understand your question, then yes - resistors are reversible, in the sense that they can be connected to the circuit in either direction. Resistors are not like diodes or capacitors. They do not have a polarity. The conduct (or resist) current equally in both directions of current flow.
• #### Do resistors add or reduce voltage?

Voltage varies directly with current. "R" is the constant of proportionality telling how much it varies. If I add in a resistor to a circuit, the voltage decreases. If you have a resistor in a circuit, with a current flowing through it, there will be a voltage dropped across the resistor (as given by Ohm's law).
• #### How does the diode work?

N-type silicon (red) has extra electrons (black). Battery connected across the p-n junction makes the diode forward biased, pushing electrons from the n-type to the p-type and pushing holes in the opposite direction. Electrons and holes cross the junction and combine.

Updated: 16th October 2019