A decrease in current.
The circuit resistance is likely to gradually drop and in such case it will cause the circuit to burn down.
heat
Another name for a circuit with low resistance and high current is a short circuit. It is dangerous because, if you have sufficient energy in the power source, you can damage components and/or cause fires.
a common cause of this type problem is corrosion at a connector.
Colector resistance in an emitter follower circuit serves to place a limit on how much current can be supplied by the transistor. Often, the resistor is sized so that a short circuit in the load does not cause the transistor to fail.
In the circuit where the DC motor is added, it was not specified whether the motor was added in series or in parallel to circuit elements. If it was added in series, it will increase circuit resistance and it will cause circuit current to go down. In parallel, the motor will reduce total circuit resistance, and circuit current will increase.
Increase current by either increasing the voltage or decreasing the resistance.
In series with the circuit and never in parallel. The reason being that it will cause the circuit total resistance to drop which will make the circuit draw excessive current. That's a short circuit actually.
The circuit resistance is likely to gradually drop and in such case it will cause the circuit to burn down.
heat
If the bulbs are in a series circuit the voltage drops at each bulb drops as additional bulbs are added. In a parallel circuit the voltage is constant no matter how many bulbs are added.
Another name for a circuit with low resistance and high current is a short circuit. It is dangerous because, if you have sufficient energy in the power source, you can damage components and/or cause fires.
corroded/dirty connections
As you add more bulbs to a series circuit that means that the bulbs are in series to one another, therefore the total resistance is the sum of the individual resistance of the bulbs. If you add bulbs of the same resistance,then the rate at which the resistance changes will increase in a constant manner provided the current source is not altered. For instance if the bulb you are using is rated 20v,60w, then the current passing via the bulbs in series is the square of the voltage divided by the power in this case the current is approximately 7amperes.
The way current (series) fuses are designed and used, they are meant to overheat and blow and cause an open circuit if the current flow through these goes above the rated value. The resistance value typically is slightly higher than the wiring and adds marginal value of series resistance to the overall circuitry. The material characteristics of fuse ensure that at regular nominal current flow the fuse does not overheat, but when larger than expected current flows it overheats, melts (or gives very high resistance/open in a resettable fuse)and causes circuit to open.
You open one of the leads of resistor connected in electronic circuit while measuring its resistance in order to not introduce error cause by other components in the circuit.
A series circuit will work if there is a closed path through which the current can pass, and a voltage source. Otherwise it won't.