"Application of Ohm's Law in Series and Parallel Circuits" Download Ohm's Law PPT (Lesson 2)

"Application of Ohm's Law in Series and Parallel Circuits" Download Ohm's Law PPT (Lesson 2)

Part One Content: Basic Knowledge Key Points

Knowledge point 1: Resistance characteristics of parallel circuits

1. As shown in the figure, when the switch S is closed and opened, the ratio of the ammeter indications is 3:1, then the ratio of the resistances of the resistors R1 and R2 is 1:2.

2. Resistors R1 and R2 are connected in parallel to the power supply. Which of the following statements is incorrect (A)

A. The total resistance of a parallel circuit is equal to the sum of the reciprocals of the resistances of each parallel conductor.

B. When R1 becomes larger, the total resistance also becomes larger

C. When the power supply voltage becomes larger, the total resistance remains unchanged

D. When the current in the main circuit changes, the total resistance remains unchanged

3. There are four groups of fluorescent lamps in the classroom, each group contains 4 lamps. Xiaowei turned on one set of fluorescent lights and felt that the brightness of the classroom was not enough. After turning on another set of lights, the classroom circuit (B)

A. The total resistance increases B. The total resistance decreases C. The total current decreases D. The total voltage increases

Knowledge point 2: The shunt rule of parallel circuits

4. (Qinghai High School Entrance Examination) As shown in the figure, it is the relationship between the current and voltage through two fixed-value resistors R1 and R2. It can be seen from the figure that when R1 and R2 are connected in parallel in a circuit, the ratio of the currents passing through the two resistors I1:I2=3:1, and the ratio of the voltages applied across the two resistors U1:U2=1:1.

5. As shown in the figure, the resistance of R1 is 6 Ω. When switch S is closed, the reading of ammeter A1 is 1.2 A and the reading of ammeter A2 is 0.3 A, then the resistance of R2 is (A)

A.18 Ω B.24 Ω C.6 Ω D.3 Ω

6. As shown in the figure, R1 and R2 are connected in parallel in a circuit with a voltage of 3 V. If only the switch S1 is closed, the ammeter reading is 0.3 A; when the switches S1 and S2 are closed at the same time, the ammeter reading is 0.5 A, then (B)

The resistance of A.R1 is 60 Ω

The resistance of B.R2 is 15 Ω

C. The current through R1 at this time is 0.5 A

D. At this time, the current through R2 is 0.3 A

PPT on the application of Ohm's law in series and parallel circuits, part 2: improvement of comprehensive capabilities

7. In the circuit as shown in the figure, R1=15 Ω and R2=10 Ω. When R1 increases to 20 Ω, the indication of the voltmeter will remain unchanged. If R1 is removed, the indication of the voltmeter will remain unchanged, and the indication of the ammeter will become smaller (choose "increase" or "unchange" for both) ” or “get smaller” ).

8. In the circuit as shown in the figure, a and b are two electricity meters, one of which is an ammeter and the other is a voltmeter. R1 and R2 are two fixed-value resistors connected in parallel, where R1=60 Ω. After the switch S is closed, the ammeter indicates 0.4 A and the voltmeter indicates 6 V. At this time, the current through resistor R2 is 0.75 times the current indication.

9. (Nanchong High School Entrance Examination) A power supply with constant voltage is connected to only one resistor R1 with a resistance value of 12 Ω at both ends, and the current is 0.5 A. If a resistor R2 with a resistance value of 8 Ω is connected in parallel to both ends of the resistor R1, the total current of the parallel circuit is 1.25 A. If R2 is changed to be connected in series with R1 in the original circuit, the current in the circuit is 0.3 A.

10. As shown in the figure, the resistance R1=R2=4 Ω, the power supply voltage remains unchanged, when S1 and S2 are both closed, the ammeter indicates 0.75 A. At this time, the circuit is a parallel circuit, and the total resistance of the circuit is 2 Ω; when S1 is closed and S2 is open, the ammeter shows 0.75 A.

11. In the circuit as shown in the figure, the power supply voltage and the resistance of the bulb remain unchanged. When the slider P of the sliding rheostat R moves to the right, which of the following judgments is correct (D)

A. The ammeter’s indication increases and the voltmeter’s indication decreases.

B. The indications of ammeter and voltmeter both decrease.

C. The reading of the ammeter increases, but the reading of the voltmeter remains unchanged.

D. The reading on the ammeter decreases, but the reading on the voltmeter remains unchanged.

12. (Changde High School Entrance Examination) As shown in the figure, R0 is a fixed value resistor, R1 is a sliding rheostat, A1 and A2 are laboratory ammeters (the terminals are marked with "-", "0.6" and "3"). After closing the switch , adjust slide P. Make the pointers of the two ammeters point to the same position. Which of the following statements is correct (D)

A. The ratio of the indications of ammeter A1 and A2 is 1:4

B. The ratio of currents passing through R0 and R1 is 4:1

C. The ratio of the voltages across R0 and R1 is 1:4

D.The ratio of the resistance values ​​of R0 and R1 is 4:1

Application of Ohm's Law in Series and Parallel Circuits PPT, Part 3: Expansion and Research Breakthroughs

15. The ammeters and voltmeters commonly used in laboratories are modified from galvanometer G (actually a small-range ammeter). Galvanometer G also has resistance and also obeys Ohm's law. There is an ammeter G with a full bias current (range) of 3.0 mA and an internal resistance of Rg=1 Ω. Xiao Ming used the physics knowledge he learned to modify the galvanometer G into a multi-purpose meter that can measure both current and voltage. The circuit principle is shown in the figure. When two terminals A and B are connected, it can be used as an ammeter with a range of 0.6 A; when two terminals A and C are connected, it can be used as a voltmeter with a range of 3 V. Find the resistances R1 and R2 Resistance size (result to three decimal places).

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