"Series and Parallel Connections of Resistors" Ohm's Law PPT Courseware

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"Series and Parallel Connections of Resistors" Ohm's Law PPT Courseware

Review questions:

1. What are the laws of current and voltage in series and parallel circuits?

Current (I) characteristics

series circuit

The current is equal everywhere in a series circuit. That is: I=I1=I2

parallel circuit

In a parallel circuit, the trunk current is equal to the sum of the branch currents. That is: I=I1+I2

Voltage (U) characteristics

series circuit

The total voltage across a series circuit and the sum of the voltages of each part of the circuit. That is: U=U1+U2

parallel circuit

In a parallel circuit, the voltages at both ends of each branch are equal. That is: U=U1=U2

1. The relationship between the total resistance and the partial resistance of the series circuit:

According to Ohm's law: U1=IR1, U2=IR2, U=IR

From U=U1+U2, we can get: IR=IR1+IR2, that is, R=R1+R2

1. The total resistance of a series circuit is equal to the sum of the series resistances;

2. Formula: R=R1+R2;

3. Rule: The total resistance after series connection is greater than any individual resistance.

4. Special case: n identical resistors R0 are connected in series, R=nR0.

Knowledge application

Example 1: A resistor R1 with a resistance of 8Ω and a resistor R2 with a resistance of 16Ω are connected in series. What is the total resistance after the series connection? If the power supply voltage is 12V, what is the current flowing through R1?

Solution: The total resistance of R1 and R2 in series:

R=R1+R2=8Ω+16Ω=24Ω

From I=U/R: the current through R1:

Exercise 1 Resistor R1 is connected in series with resistor R2 with a resistance of 36Ω. It is known that the total resistance is 50Ω. Find the resistance of resistor R1? If the current through the two resistors is 100mA, what are the voltage U1 across R1 and the power supply voltage?

Known: R2=36Ω, R=50Ω, I=100mA=0.1A

Request: R1 U1 U

Solution: From R=R1+R2, we get R1=R-R2=50Ω-36Ω=14Ω

by ohm's law

U1=I·R1=0.1A×36Ω=3.6V U=I·R=0.1A×50Ω=5V

Answer: slightly

2. The relationship between the total resistance and the partial resistance of the parallel circuit:

1. The reciprocal of the total resistance of a parallel circuit is equal to the sum of the reciprocals of the parallel resistances.

2. Formula:

When multiple resistors are connected in parallel, the total cross-sectional area of ​​the resistors is larger than that of any one resistor.

3. Rule: The resistance becomes smaller as the resistance increases, and the total resistance in parallel is less than any one partial resistance;

4. Special case: n identical resistors R0 are connected in parallel, R = R0 / n.

Want to discuss:

When the resistance of one branch in a parallel circuit becomes larger, how does the total resistance in the circuit change? How will the current in the main circuit change, and how will the current and voltage in the other branch change?

The total resistance increases, the current in the main circuit becomes smaller, and the current and voltage of the other branch remain unchanged.

Regardless of whether it is a parallel or series circuit, as long as one of the resistors becomes larger, the total resistance in the circuit becomes larger.

3. Ohm’s Law Calculation

3. There is a light bulb L and a fixed-value resistor R connected in series in a circuit with a power supply voltage of 6V. The current through the light bulb L is 0.4A, and the voltage across the resistor R is 2V. Find: the resistance value of the bulb L and the resistance value of the resistor R.

4. The voltage of a small light bulb when it lights up normally is 4v, and the resistance is 10Ω. If you only have a power supply with a voltage of 12v at hand, how should you design the circuit to make the small light bulb light up normally?

5. As shown in the picture on the right, the resistor R1 is 10 Ω, the power supply voltage U=12V, the maximum resistance of the sliding rheostat R2 is 50Ω, when the sliding plate P of the sliding rheostat moves from the right end to the left end, the indication of the voltmeter will be _______ . The reading on the ammeter will be __________.

Find the changing range of ammeter and voltmeter.

In order to keep the voltmeter and current indications from exceeding their small ranges, the changing range of the sliding rheostat is _____Ω to ______ Ω.

practise:

1. You are given three fixed-value resistors, each of which is 10Ω. Please connect them to the circuit in different ways, draw the circuit diagram, and calculate the corresponding total resistance value? (write down the calculation process)

2. There is a soldering iron with a resistance of 440Ω and a voltage of 220V during normal operation. Now connect it to a 380V power supply. In order to work normally, how big a resistor should be connected to it? What is the current during normal operation?

3. As shown in the figure, the power supply voltage remains unchanged, R1=7Ω, R2=8Ω, and the voltage indicates 4V after closing the switch. What is the power supply voltage? (solve using two methods)

4. As shown in the figure, when the switch is closed, the indications of A1 and A2 are 0.6A and 1A respectively, and R2=6Ω. Find: the resistance of R1 and the power supply voltage.

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"Series and Parallel Connections of Resistors" Ohm's Law PPT Courseware 2:

"Resistors in Series and Parallel" Ohm's Law PPT Courseware 2 Review Questions: 1. Do you know the verbal expression and alphabetical expression of Ohm's Law? (1) Verbal expression: The current in a conductor is proportional to the voltage at both ends of the conductor, and is proportional to the voltage at both ends of the conductor. is inversely proportional to the resistance. (2) Words..

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Update Time: 2024-10-03

This template belongs to Physics courseware Lu Jiao Edition Ninth Grade Physics Volume 1 industry PPT template

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