Adjustable Small Light - Variable Resistor Course Presentation

  Adjustable resistor changes the circuit current. Observe the adjustable resistor carefully and study its structure and the role of each part.

 Explore the law and think: how to connect a variable resistor correctly in a circuit, how to adjust the brightness of a small light, do you know how to control the brightness of a light bulb? In a theater performance, we see that the lighting gradually becomes darker and then gradually becomes brighter. Now we have two light bulbs that have been connected to the circuit, how can we change their brightness?

 Resistance change and current change: How can we change the resistance of a conductor?

Which method is simple? How can I change the size of the current?

  Principle: By changing the number of turns in a variable resistor connected to a circuit, the resistance in the circuit is altered.

The principle of a variable resistor:

By changing the length of the resistive wire in the circuit to alter the resistance.

The method of using a variable resistor:

The resistance wire of the variable resistor is not connected to the circuit, so it cannot change the resistance and thus the current. This is an incorrect usage.

 It is equivalent to connecting a constant resistance to a circuit, and it does not play the role of changing the resistance to change the current.

Experimental Report

As the resistance coil gets longer, the resistance increases, the current decreases, and the light becomes dimmer.

As the resistance coil becomes shorter, the resistance decreases, the current increases, and the light becomes brighter.

Explore: What are the patterns between the connection methods of variable resistors?

Series connection in the circuit discussion and exchange of large resistance allow the passage of large current