What is the use of resistor in an electric circuit

Hi,

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.

Resistors are most commonly used as a voltage divider &/or as a current limiter.

Consider two 50 ohm resistors connected in series, both being connected across a 20 volt power supply.

The voltage at the midpoint of the resistors is 10 volts, its tempting to say? Let's see in a bit.

Two 50 ohm resistors in series add up to 100 ohms.

Ohms* law says that R=100 ohms placed across E=20 volts will draw I=0.2 amp

*E = IR, so I=E/R =20/100= 0.2 amp

Since each resistor is drawing 0.2 amp, each resistor develops E=IR, E= (0.2)(50) = 10 volts across it.

Since our circuit consists of 2 resistors in series, the voltage across both is 10 + 10 = 20 volts, with 10 volts at their junction, as we assumed.

Finally, by this choice of resistor values, we have limited the current in this circuit to 0.2 amp…

This circuit provides a way of dividing a voltage in half, or providing exactly 10 volts (e.g. to charge a 9V battery) from a 20 volt supply.

Resistors can be a problem and asset in an IC circuit. You can use resistors to amplify small signals or they can be parasitic making IC circuits inefficient by dissipating more heat or power. If you have high parasitic RC constant, which is a time constant, you slow the IC circuit down. This question is somewhat general because resistors can be used inside and outside of an IC chip. You can have resistors on PCB board for example, and there are some advantages of using resistors on PCB. For example, you can reduce the costs on the board instead of on the chip.

Hope this helps.