What is the point of a resistor in a circuit?

Question

what is the point of a resistor in a circuit?

( I am doing syst tech and I need the answer ASAP so if anybody knows can you please tell me in simple words the web sites I have looked at are making no sence to me at all )

Answer 1

Resistors can do one of two things:

1.  In series they can drop the voltage

2.  In parallel they can split the current

I will explain resistors in series.

Let's say you have a 5VDC (five volts direct current) supply.

V = Supply voltage

V1 = Voltage drop across resistor #1

V2 = Voltage drop across resistor #2

R1 = Resistance of resistor #1 (Ohms)

R2 = Resistance of resistor #2 (Ohms)

i = current (amps)

For a series circuit:  V1 + V2 = V

Ohms Law:  V = iR

For a circuit with only one resistor:  R1 = 2

According to Ohms Law:

i = V/R = 5/2 = 2.5Amps

The circuit would have 2.5 amps of current and the voltage drop across the single resistor would be 5V.

Now look at the case with two resistors in the circuit: R1 = 2, R2 = 3

i=V/(R1 + R2) = 5/(2 + 3) = 1A

V1 = i(R1) = (1)(2) = 2V

V2 = i(R2) = (1)(3) = 3V

Now you have a circuit that will measure 5V at the supply, 2V across R1, and 3V across R2.  These circuits can be used when you want to run a device that will burn up at higher voltages.

Answer 2

Simple answer - to limit current.

Answer 3

A resistor limits the current that can flow in an electrical circuit.

Or in even more simple terms:

Imagine a water pipe of large diameter, suddenly that pipe becomes very thin, and then goes back to its original diameter. The amount of water that can flow (the "current") is limited by the small diameter piece (the "resistor"), but the amount also depends on the water pressure (the "voltage").

Hence current = voltage div.by resistor