Physics puzzles

There are two resistors R① and R②, and R①=nR②. After being connected in parallel and connected to a circuit, the current in the main circuit is I, and the currents in R① and R② are I① and I② respectively. The following relationships The wrong ones are: A: 1 B: I①＝-I② I＝（n＋1）I② n C: 1 D: n I①＝ ＿＿I I②＝－－－I n＋1 n＋1

If the two are determined If the value resistors R1 and R2 are connected to the power supply in a certain way, the electric power consumed by R1 is 9 watts; if the two resistors are connected in another way and still connected to the power supply, the electric power consumed by R1 is 16 watts. Watts and the current through R2 is 4A, then what are the power supply voltage and the resistance values ??of R1 and R2? (Please indicate the calculation process)

1. The resistance of a section of copper wire is R, the voltage at both ends is U, and the intensity of the passing current is I. The correct one of the following statements is 〔 〕

A. R is determined by the length and cross-sectional area of ??the copper wire

B. The size of R is related to U

C. The resistance of the copper wire hinders the passage of current

D. The size of R has nothing to do with I

2. If two resistors with exactly the same resistance value are connected in parallel and the total resistance is 10 ohms, then the total resistance of connecting them in series is [ ]

A. 5 ohms b． 10 ohms

C. 20 ohms D. 40 ohms

3. The resistance of a wire is R. After folding it in half and dividing it into two sections of equal length, and then connecting the two sections in parallel, the resistance is []

A. R/4 B.R/2 C. R/2

4. Four resistors, the resistance values ??are all R. If they are connected in parallel, the total resistance is []

A. 4R B. R/4 C. 4/R D. 2R

5. If two resistance wires made of the same material with equal lengths and different cross-sectional areas are connected in series in a circuit, the thick resistance wire will be thick [ ]

A. The current intensity is larger B. The current intensity is small

C. The voltage is larger D. The voltage is small

6. Among the following four pairs of parallel resistors, the one with the smallest total resistance is 〔 〕

A. Two 4Ω B. One 4Ω, one 6Ω

C. One 1Ω, one 8Ω D. One is 2Ω, the other is 7Ω

7. There are three resistors today. Their resistance values ??are a ohm, b ohm, and c ohm respectively, where a>b>c. When they are connected in parallel, the total resistance is R. Their size relationship, which of the following judgments is correct? 〔 〕

A. c

C． R may be equal to b D. R

8. Two resistors of equal resistance, each with a resistance value R.

Now increase one of the resistances and decrease the other resistance, then the total resistance after parallel connection will be [ ]

A. Greater than R B. Less than R

C. Still equal to R D. Unable to determine

9. There is a resistor wire. When a voltage of 1 volt is applied to both ends of the wire, the measured resistance value is 0.5 ohm. If a voltage of 10 volts is applied to both ends of the wire, the resistance value should be [ ]

A. 0.5 ohm B. 5 ohms

C. 0.05 ohm D. 20 ohms

10. The resistance of resistor R1 is smaller than that of resistor R2. After connecting them in parallel, the total resistance is [ ]

A. Both smaller than R1 and smaller than R2 B. Both greater than R1 and greater than R2

C. Less than R2 and greater than R1 D. Equal to the sum of R1 and R2

12. Repairing electrical appliances requires a 150-ohm resistor, but there are only one resistor with a resistance value of 100 ohms, 200 ohms, and 600 ohms. The alternative method is〔〕

A. Connect the 200 ohm resistor and the 600 ohm resistor in series

B. Connect the 100 ohm resistor and the 200 ohm resistor in series

C. Connect the 100 ohm resistor and the 200 ohm resistor in parallel

D. Connect the 200 ohm resistor and the 600 ohm resistor in parallel

13. The voltage across the conductor is 4 volts, and the current intensity passing through it is 0.8 amps. If the voltage across the conductor is increased to 6 volts, then the resistance and current intensity of the conductor are respectively〔〕

A. 5 ohms, 1.2 amps B. 5 ohms, 2 amps

C． 7.5 ohms, 0.8 amps D. 12.5 ohms, 0.8 amps

1. There is a resistor R1 with a resistance of 10 ohms. The maximum current intensity allowed to pass through is 100 mA. If you want to connect this resistor to a 1.1 amp circuit, What should be done

? (Draw the circuit diagram and calculate the value)

2. In the circuit shown in the figure, the power supply voltage is 6 volts and the resistance of the resistor R is 10 Ohm, the maximum resistance of the sliding rheostat is 50 Ohm. When the sliding plate P of the rheostat slides from A to B,

What is the range of change of the voltmeter's indication?

3. There is a resistor of only 200 ohms, and the maximum current intensity allowed to pass through is 0.2 A. If it is connected to a 110-volt circuit, can it work normally? In order to make it work normally, it should be in the circuit

How to connect a resistor with a large resistance in the circuit?

4. There are two resistors connected in series in the circuit. It is known that R1:R2=3:2. If the voltage at both ends of the circuit is 15 volts, then , what is the voltage across R1?

5. In the figure, the power supply voltage U=6 volts, R1=R2=15 ohms, when the slider P is placed at both ends a and b of the varistor , what are the readings of the ammeter and voltmeter?

6. In the circuit as shown in the figure, R1=6 ohms, R2=8 ohms, and the power supply voltage is 12 volts. Find: (1 ) When K2 is open and K1 and K3 are closed, what is the current intensity through R1 and R2? (2) When K2 is closed and K1 and K3 are open, what is the current intensity at both ends of the resistors R1 and R2? What are the voltages?

7. The resistance of an electrical appliance is 20 ohms. When working normally, the current intensity passing through it is 0.5 amps.

(1) When this electrical appliance is connected to a 12-volt power supply, what is the intensity of the current passing through it? Try to analyze whether the electrical appliance can work normally at this time? (2) If it is connected to a 12-volt power supply, On the power supply, how big a resistor needs to be connected in series to make it work properly?

8. As shown in the figure, R1=30 ohms, and the slider P of the sliding rheostat is in the middle point, the voltmeter indicates 3 volts, and when the slider P is at terminal b, the voltmeter indicates 4.5 volts.

Find the power supply voltage and the resistance of the sliding rheostat?

9. As shown in the figure, it is known that the power supply voltage is 6 volts, R1=10 ohms, the reading of A1 is 0.5 amps, R2=20 ohms, what is the reading of A2?

10 , As shown in the figure, the resistor R1 = 40 ohms is connected in parallel with R2 on the power supply. When the switch S is turned off, the current value is 1/3 of the original value. Find the value of R2?

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