What is the change of the total resistance during the movement of the sliding rheostat in the divider circuit? Tell me why

What is the change of the total resistance during the movement of the sliding rheostat in the divider circuit? Tell me why

The total resistance of the sliding rheostat does not change, while the resistance of the moving end changes to one of the other two ends. The popular understanding is that a piece of bread should be cut into two pieces. The process of moving the sliding end is changing the proportion of the two pieces. However, no matter how to change the position of the knife, the two pieces together are still the same big bread

When the sliding rheostat is correctly connected into the circuit, no matter how to move the sliding contact, can the resistance of the consumer in the circuit be changed?

The resistance is generally considered to be constant unless the temperature is changed. The sliding rheostat can only change its own resistance so as to change the current in the circuit. According to the square r of q = I, the smaller the resistance of the sliding rheostat in the circuit is, the larger the current is, the higher the temperature is, and the resistance also increases, but not too much

As shown in the circuit diagram, set the power supply voltage and bulb resistance unchanged. Close switch S. in the process of sliding rheostat slide movement, the minimum indication of ammeter is 0.2A, the maximum indication of voltmeter is 4V, and the ratio of maximum power and minimum power of lamp L is 9:4, then ()
A. The power supply voltage is 6vb. The resistance of the lamp is 40 Ω C. the power supply voltage is 4vd. The maximum power consumption of the circuit is 2.4W

The bulb and the sliding rheostat are connected in series in the circuit. The ammeter measures the current of the circuit. The resistance of the sliding rheostat connected to the circuit is the largest when the current is the smallest. The voltmeter measures the voltage of the sliding rheostat. When the voltage is the largest, the resistance of the sliding rheostat connected to the circuit is the largest. The resistance of the bulb remains unchanged. The maximum power of the lamp L is u2rl, the minimum power of the lamp L is (U − 4V) 2RL, and the maximum power of the lamp L is (U − 4V) 2rl The ratio of maximum power to minimum power is 9:4, so UU − 4V = 32, i.e. u = 12V, so a is wrong, C is wrong. RL = Uli = 12V − 4v0.2a = & nbsp; 40 Ω, so B is correct. When the resistance of sliding rheostat is the smallest, the circuit consumes the most power. P = u2rl = (12V) 240 Ω = 3.6W, so D is wrong. So select B

As shown in the circuit diagram, set the power supply voltage and bulb resistance unchanged. Close switch S. in the process of sliding rheostat slide movement, the minimum indication of ammeter is 0.2A, the maximum indication of voltmeter is 4V, and the ratio of maximum power and minimum power of lamp L is 9:4, then ()
A. The power supply voltage is 6vb. The resistance of the lamp is 40 Ω C. the power supply voltage is 4vd. The maximum power consumption of the circuit is 2.4W

The bulb and the sliding rheostat are connected in series in the circuit. The ammeter measures the current of the circuit. The resistance of the sliding rheostat connected to the circuit is the largest when the current is the smallest. The voltmeter measures the voltage of the sliding rheostat. When the voltage is the largest, the resistance of the sliding rheostat connected to the circuit is the largest. The resistance of the bulb remains unchanged. The maximum power of the lamp L is u2rl, the minimum power of the lamp L is (U − 4V) 2RL, and the maximum power of the lamp L is (U − 4V) 2rl The ratio of maximum power to minimum power is 9:4, so UU − 4V = 32, i.e. u = 12V, so a is wrong, C is wrong. RL = Uli = 12V − 4v0.2a = & nbsp; 40 Ω, so B is correct. When the resistance of sliding rheostat is the smallest, the circuit consumes the most power. P = u2rl = (12V) 240 Ω = 3.6W, so D is wrong. So select B