Experimental steps and circuit diagram of measuring resistance by volt ampere method and safety resistance method (only one ammeter and one custom resistance are required)

Connect 1. S to 1, and record the indication I1 of the ammeter
&Nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 2. S is connected to 2, and the current representation number I2 is recorded
R=I1R1/I2

How to select resistance according to resistance power in circuit design

Under 1 / 8W, 0805 chip resistor is used, and 1206 chip resistor can achieve 1 / 4W
RJ series metal film resistors can be used below 1W
5W can use ry series metal oxide film resistor
Over 5W, it's better to use RX series wire wound resistor, or cement resistor
If there is pulse power, the power should be higher

How does the sliding rheostat move to the right? How does the voltage, resistance and current change? How does the brightness of the appliance change?

When using the sliding rheostat, we can't just look at whether the slide is right or left. What we need to see is whether it is farther away or closer to the lower terminal. The closer it is, the smaller the resistance is. The farther it is, the greater the resistance is

In a series circuit, if the resistance of one of the consumers increases, will the total resistance increase? In a parallel circuit, the resistance of the branch increases
What is the change of the total resistance

Series circuit R = R1 + R2 +... + RN
When one resistance increases, the total resistance increases
Parallel circuit 1 / r = 1 / R1 + 1 / r2 +... + 1 / RN
When one resistance on the branch increases, the total resistance increases

Experimental steps and circuit diagram of measuring resistance by volt ampere method and safety resistance method (only one ammeter and one custom resistance are required)