Why do we connect a resistor to a battery source in a circuit?
In simple to current limit, to decrease current, to regulate voltage.
Resistors are not added to the circuit randomly. A designer has an objective in mind when designing a circuit. When the design requires resistors, it adds them if necessary. This also applies to other circuit elements, such as capacitors, icons, etc. it is not mandatory to use a resistor in each battery circuit; however, for a desirable nominal current in the circuit, it is widely used, the use of the resistor dissipated and strongly discouraged in the circuit, it is only used to reduce the cost of the circuit.
When learning ohm law, an exercise is defined with a battery of volts, with a resistance of r ohms. The current I is v / r
If you want to create a lower voltage, two resistors in series with the battery form a voltage divider. These are simple examples used to create the conditions necessary for the operation of electronic circuits.
We do not do it. We connect any component of a circuit to perform a function. You only indicated a battery and a resistance. And do not bother to do it. We do not usually connect a battery to a resistor.
I used resistors as a load to measure the actual capacity of an amp-hour battery to determine if it was still good.
Again, there is no reason to say in general to put these two together
You want to drive a single led? You may need some resistance to limit the current but say that you only drive the motor of your cup with automatic stirring, it is not necessary to put a resistance inside.
If you have a specific circuit and you have questions about some resistors, post it and many people will help you find the reason for its existence on this circuit.
Resistors are not needed in all circuits; often any additional resistance is detrimental to performance. Sometimes, resistors are needed, such as with a led bulb and a battery, to limit or reduce the current through the bulb.
In general, the resistors are used to limit or reduce the current or to cause a voltage reduction. They have other more complex functions, such as the intentional dissipation of electrical energy in the form of heat.
Sometimes resistance or resistance is needed. A resistance has a definite relation with a system by an electric law called ohm’s law. A resistance to a voltage and a current determined by the law of ohm. The current passing through a resistor and the voltage passing through it also produce heat, which wastes electrical energy in the form of heat.
The short is that the resistors are used to reduce the current flowing through the resistance path, to cause a voltage drop in the resistance path or to dissipate the electrical current (despite heating). As long as the current goes through a resistance, it always does the three, no matter what is most useful or desirable.